Enable header ids to be generated in markdown

...feature_flags/gitlab_com_derisk/native_header_anchors.yml

ee/lib/ee/banzai/filter/sanitization_filter.rb

ee/spec/helpers/vulnerabilities_helper_spec.rb

ee/spec/requests/api/graphql/vulnerabilities/fields_spec.rb

glfm_specification/output_example_snapshots/html.yml

...specification/output_example_snapshots/snapshot_spec.html

glfm_specification/output_spec/spec.html

lib/banzai/filter/markdown_engines/glfm_markdown.rb

lib/banzai/filter/sanitization_filter.rb

lib/banzai/filter/table_of_contents_filter.rb

lib/banzai/filter/table_of_contents_tag_filter.rb

lib/banzai/pipeline/description_pipeline.rb

.../lib/banzai/filter/markdown_engines/glfm_markdown_spec.rb

spec/lib/banzai/filter/sanitization_filter_spec.rb

spec/lib/banzai/filter/table_of_contents_filter_spec.rb

spec/lib/banzai/filter/table_of_contents_tag_filter_spec.rb