Quarantine failing tests

qa/qa/specs/features/browser_ui/3_create/merge_request/create_merge_request_spec.rb

 # frozen_string_literal: true
 module QA
-  context 'Create' do
+  # Failure issue: https://gitlab.com/gitlab-org/quality/staging/issues/50
+  context 'Create', :quarantine do
     describe 'Merge request creation' do
       it 'user creates a new merge request', :smoke do
         Runtime::Browser.visit(:gitlab, Page::Main::Login)

qa/qa/specs/features/browser_ui/3_create/snippet/create_snippet_spec.rb

 # frozen_string_literal: true
 module QA
-  context 'Create', :smoke do
+  # Failure issue: https://gitlab.com/gitlab-org/quality/staging/issues/49
+  context 'Create', :smoke, :quarantine do
     describe 'Snippet creation' do
       it 'User creates a snippet' do
         Runtime::Browser.visit(:gitlab, Page::Main::Login)

qa/qa/specs/features/browser_ui/4_verify/ci_variable/add_ci_variable_spec.rb

 # frozen_string_literal: true
 module QA
-  context 'Verify' do
+  # Failure issue: https://gitlab.com/gitlab-org/quality/nightly/issues/91
+  context 'Verify', :quarantine do
     describe 'CI variable support' do
       it 'user adds a CI variable' do
         Runtime::Browser.visit(:gitlab, Page::Main::Login)