Fix deprecated usagepatterns of rubocop

rubocop/cop/gitlab/rails_logger.rb

@@ -5,7 +5,7 @@
 module RuboCop
   module Cop
     module Gitlab
-      class RailsLogger < ::RuboCop::Cop::Cop
+      class RailsLogger < ::RuboCop::Cop::Base
         include CodeReuseHelpers
         # This cop checks for the Rails.logger log methods in the codebase

rubocop/cop/migration/change_column_null_on_high_traffic_table.rb

@@ -5,7 +5,7 @@
 module RuboCop
   module Cop
     module Migration
-      class ChangeColumnNullOnHighTrafficTable < RuboCop::Cop::Cop
+      class ChangeColumnNullOnHighTrafficTable < RuboCop::Cop::Base
         include MigrationHelpers
         MSG = 'Using `change_column_null` migration helper is risky for high-traffic tables. ' \

rubocop/cop/qa/feature_flags.rb

@@ -23,7 +23,7 @@ module QA
       #   describe 'some test' do
       #     before do
       #       Runtime::Feature.enable(:flag)
-      class FeatureFlags < RuboCop::Cop::Cop
+      class FeatureFlags < RuboCop::Cop::Base
         APPLY_MESSAGE = "Apply the `feature_flag: { name: :flag }` metadata to the test to use `%{feature}` in " \
           "end-to-end tests."
         BLOCK_MESSAGE = "Feature flags must specify a name. Use a block with `feature_flag: { name: :flag }` instead."