Fix Rubocop offenses

lib/gitlab/background_migration/prepare_untracked_uploads.rb

@@ -91,13 +91,13 @@ module Gitlab
         table_columns_and_values = 'untracked_files_for_uploads (path, created_at, updated_at) VALUES (?, ?, ?)'
         sql = if Gitlab::Database.postgresql?
-          "INSERT INTO #{table_columns_and_values} ON CONFLICT DO NOTHING;"
-        else
-          "INSERT IGNORE INTO #{table_columns_and_values};"
-        end
+                "INSERT INTO #{table_columns_and_values} ON CONFLICT DO NOTHING;"
+              else
+                "INSERT IGNORE INTO #{table_columns_and_values};"
+              end
         timestamp = Time.now.utc.iso8601
-        sql = ActiveRecord::Base.send(:sanitize_sql_array, [sql, file_path, timestamp, timestamp])
+        sql = ActiveRecord::Base.send(:sanitize_sql_array, [sql, file_path, timestamp, timestamp]) # rubocop:disable GitlabSecurity/PublicSend
         ActiveRecord::Base.connection.execute(sql)
       end

spec/lib/gitlab/background_migration/populate_untracked_uploads_spec.rb

@@ -215,7 +215,6 @@ describe Gitlab::BackgroundMigration::PopulateUntrackedUploads::UntrackedFile do
     context 'for a project Markdown attachment (notes, issues, MR descriptions) file path' do
       let(:model) { create(:project) }
-      let(:expected_upload_attrs) { {} }
       # UntrackedFile.path is different than Upload.path
       let(:untracked_file) { create_untracked_file("/#{model.full_path}/#{model.uploads.first.path}") }
@@ -228,7 +227,7 @@ describe Gitlab::BackgroundMigration::PopulateUntrackedUploads::UntrackedFile do
         untracked_file
         # Save the expected upload attributes
-        expected_upload_attrs = model.reload.uploads.first.attributes.slice('path', 'uploader', 'size', 'checksum')
+        @expected_upload_attrs = model.reload.uploads.first.attributes.slice('path', 'uploader', 'size', 'checksum')
         # Untrack the file
         model.reload.uploads.delete_all
@@ -239,8 +238,7 @@ describe Gitlab::BackgroundMigration::PopulateUntrackedUploads::UntrackedFile do
           untracked_file.add_to_uploads
         end.to change { model.reload.uploads.count }.from(0).to(1)
-        hex_secret = untracked_file.path.match(/\/(\h+)\/rails_sample.jpg/)[1]
-        expect(model.uploads.first.attributes).to include(expected_upload_attrs)
+        expect(model.uploads.first.attributes).to include(@expected_upload_attrs)
       end
     end
   end

spec/lib/gitlab/background_migration/prepare_untracked_uploads_spec.rb

@@ -36,7 +36,7 @@ describe Gitlab::BackgroundMigration::PrepareUntrackedUploads, :migration, :side
       stub_application_setting(hashed_storage_enabled: true)
-        # Markdown upload after enabling hashed_storage
+      # Markdown upload after enabling hashed_storage
       UploadService.new(project2, uploaded_file, FileUploader).execute
     end

spec/migrations/track_untracked_uploads_spec.rb

@@ -42,7 +42,7 @@ describe TrackUntrackedUploads, :migration, :sidekiq, :temp_table_may_drop do
     it 'has a path field long enough for really long paths' do
       migrate!
-      component = 'a'*255
+      component = 'a' * 255
       long_path = [
         'uploads',