Add frozen_string_literal to serializer specs

https://gitlab.com/gitlab-org/gitlab/issues/27703

spec/serializers/analytics_build_entity_spec.rb

+# frozen_string_literal: true
+
 require 'spec_helper'
 describe AnalyticsBuildEntity do

spec/serializers/analytics_build_serializer_spec.rb

+# frozen_string_literal: true
+
 require 'spec_helper'
 describe AnalyticsBuildSerializer do

spec/serializers/analytics_issue_entity_spec.rb

+# frozen_string_literal: true
+
 require 'spec_helper'
 describe AnalyticsIssueEntity do

spec/serializers/analytics_issue_serializer_spec.rb

+# frozen_string_literal: true
+
 require 'spec_helper'
 describe AnalyticsIssueSerializer do

spec/serializers/analytics_merge_request_serializer_spec.rb

+# frozen_string_literal: true
+
 require 'spec_helper'
 describe AnalyticsMergeRequestSerializer do

spec/serializers/analytics_stage_serializer_spec.rb

+# frozen_string_literal: true
+
 require 'spec_helper'
 describe AnalyticsStageSerializer do

spec/serializers/analytics_summary_serializer_spec.rb

+# frozen_string_literal: true
+
 require 'spec_helper'
 describe AnalyticsSummarySerializer do

spec/serializers/blob_entity_spec.rb

+# frozen_string_literal: true
+
 require 'spec_helper'
 describe BlobEntity do

spec/serializers/build_action_entity_spec.rb

+# frozen_string_literal: true
+
 require 'spec_helper'
 describe BuildActionEntity do

spec/serializers/build_artifact_entity_spec.rb

+# frozen_string_literal: true
+
 require 'spec_helper'
 describe BuildArtifactEntity do

spec/serializers/build_details_entity_spec.rb

+# frozen_string_literal: true
+
 require 'spec_helper'
 describe BuildDetailsEntity do

spec/serializers/build_serializer_spec.rb

+# frozen_string_literal: true
+
 require 'spec_helper'
 describe BuildSerializer do

spec/serializers/cluster_application_entity_spec.rb

+# frozen_string_literal: true
+
 require 'spec_helper'
 describe ClusterApplicationEntity do

spec/serializers/cluster_basic_entity_spec.rb

+# frozen_string_literal: true
+
 require 'spec_helper'
 describe ClusterBasicEntity do

spec/serializers/cluster_entity_spec.rb

+# frozen_string_literal: true
+
 require 'spec_helper'
 describe ClusterEntity do

spec/serializers/cluster_serializer_spec.rb

+# frozen_string_literal: true
+
 require 'spec_helper'
 describe ClusterSerializer do

spec/serializers/commit_entity_spec.rb

+# frozen_string_literal: true
+
 require 'spec_helper'
 describe CommitEntity do

spec/serializers/container_repository_entity_spec.rb

+# frozen_string_literal: true
+
 require 'spec_helper'
 describe ContainerRepositoryEntity do

spec/serializers/container_tag_entity_spec.rb

+# frozen_string_literal: true
+
 require 'spec_helper'
 describe ContainerTagEntity do

spec/serializers/deploy_key_entity_spec.rb

+# frozen_string_literal: true
+
 require 'spec_helper'
 describe DeployKeyEntity do