RSpec zero monkey patching mode

The plan for RSpec 4.0 is to disable monkey patching, reference:
https://rspec.info/blog/2013/07/the-plan-for-rspec-3/#zero-monkey-patching-mode
https://relishapp.com/rspec/rspec-core/docs/configuration/zero-monkey-patching-mode

This commit stops using RSpec monkey patching in several specs.

spec/models/protectable_dropdown_spec.rb

@@ -2,7 +2,7 @@
 require 'spec_helper'
-describe ProtectableDropdown do
+RSpec.describe ProtectableDropdown do
   let(:project) { create(:project, :repository) }
   let(:subject) { described_class.new(project, :branches) }

spec/models/protected_branch/merge_access_level_spec.rb

@@ -2,6 +2,6 @@
 require 'spec_helper'
-describe ProtectedBranch::MergeAccessLevel do
+RSpec.describe ProtectedBranch::MergeAccessLevel do
   it { is_expected.to validate_inclusion_of(:access_level).in_array([Gitlab::Access::MAINTAINER, Gitlab::Access::DEVELOPER, Gitlab::Access::NO_ACCESS]) }
 end

spec/models/protected_branch/push_access_level_spec.rb

@@ -2,6 +2,6 @@
 require 'spec_helper'
-describe ProtectedBranch::PushAccessLevel do
+RSpec.describe ProtectedBranch::PushAccessLevel do
   it { is_expected.to validate_inclusion_of(:access_level).in_array([Gitlab::Access::MAINTAINER, Gitlab::Access::DEVELOPER, Gitlab::Access::NO_ACCESS]) }
 end

spec/models/protected_branch_spec.rb

@@ -2,7 +2,7 @@
 require 'spec_helper'
-describe ProtectedBranch do
+RSpec.describe ProtectedBranch do
   subject { build_stubbed(:protected_branch) }
   describe 'Associations' do

spec/models/protected_tag_spec.rb

@@ -2,7 +2,7 @@
 require 'spec_helper'
-describe ProtectedTag do
+RSpec.describe ProtectedTag do
   describe 'Associations' do
     it { is_expected.to belong_to(:project) }
   end

spec/models/push_event_payload_spec.rb

@@ -2,7 +2,7 @@
 require 'spec_helper'
-describe PushEventPayload do
+RSpec.describe PushEventPayload do
   it_behaves_like 'having unique enum values'
   describe 'saving payloads' do

spec/models/push_event_spec.rb

@@ -2,7 +2,7 @@
 require 'spec_helper'
-describe PushEvent do
+RSpec.describe PushEvent do
   let(:payload) { PushEventPayload.new }
   let(:event) do

spec/models/readme_blob_spec.rb

@@ -2,7 +2,7 @@
 require 'spec_helper'
-describe ReadmeBlob do
+RSpec.describe ReadmeBlob do
   include FakeBlobHelpers
   describe 'policy' do

spec/models/redirect_route_spec.rb

@@ -2,7 +2,7 @@
 require 'spec_helper'
-describe RedirectRoute do
+RSpec.describe RedirectRoute do
   let(:group) { create(:group) }
   let!(:redirect_route) { group.redirect_routes.create(path: 'gitlabb') }

spec/models/releases/evidence_spec.rb

@@ -2,7 +2,7 @@
 require 'spec_helper'
-describe Releases::Evidence do
+RSpec.describe Releases::Evidence do
   let_it_be(:project) { create(:project) }
   let(:release) { create(:release, project: project) }

spec/models/releases/link_spec.rb

@@ -2,7 +2,7 @@
 require 'spec_helper'
-describe Releases::Link do
+RSpec.describe Releases::Link do
   let(:release) { create(:release, project: project) }
   let(:project) { create(:project) }

spec/models/releases/source_spec.rb

@@ -2,7 +2,7 @@
 require 'spec_helper'
-describe Releases::Source do
+RSpec.describe Releases::Source do
   let_it_be(:project) { create(:project, :repository, name: 'finance-cal') }
   let(:tag_name) { 'v1.0' }

spec/models/remote_mirror_spec.rb

@@ -2,7 +2,7 @@
 require 'spec_helper'
-describe RemoteMirror, :mailer do
+RSpec.describe RemoteMirror, :mailer do
   include GitHelpers
   describe 'URL validation' do

spec/models/repository_language_spec.rb

@@ -2,7 +2,7 @@
 require 'spec_helper'
-describe RepositoryLanguage do
+RSpec.describe RepositoryLanguage do
   let(:repository_language) { build(:repository_language) }
   describe 'associations' do

spec/models/repository_spec.rb

@@ -2,7 +2,7 @@
 require 'spec_helper'
-describe Repository do
+RSpec.describe Repository do
   include RepoHelpers
   include GitHelpers

spec/models/resource_milestone_event_spec.rb

@@ -2,7 +2,7 @@
 require 'spec_helper'
-describe ResourceMilestoneEvent, type: :model do
+RSpec.describe ResourceMilestoneEvent, type: :model do
   it_behaves_like 'a resource event'
   it_behaves_like 'a resource event for issues'
   it_behaves_like 'a resource event for merge requests'

spec/models/resource_state_event_spec.rb

@@ -2,7 +2,7 @@
 require 'spec_helper'
-describe ResourceStateEvent, type: :model do
+RSpec.describe ResourceStateEvent, type: :model do
   subject { build(:resource_state_event, issue: issue) }
   let(:issue) { create(:issue) }

spec/models/review_spec.rb

@@ -2,7 +2,7 @@
 require 'spec_helper'
-describe Review do
+RSpec.describe Review do
   describe 'associations' do
     it { is_expected.to belong_to(:author).class_name('User').with_foreign_key(:author_id).inverse_of(:reviews) }
     it { is_expected.to belong_to(:merge_request).inverse_of(:reviews).touch(false) }

spec/models/route_spec.rb

@@ -2,7 +2,7 @@
 require 'spec_helper'
-describe Route do
+RSpec.describe Route do
   let(:group) { create(:group, path: 'git_lab', name: 'git_lab') }
   let(:route) { group.route }

spec/models/sent_notification_spec.rb

@@ -2,7 +2,7 @@
 require 'spec_helper'
-describe SentNotification do
+RSpec.describe SentNotification do
   let_it_be(:user) { create(:user) }
   let_it_be(:project) { create(:project) }