Remove the glfm_specification testing files

.gitlab/CODEOWNERS

.rubocop_todo/layout/empty_line_after_magic_comment.yml

...todo/layout/line_end_string_concatenation_indentation.yml

.rubocop_todo/lint/assignment_in_condition.yml

.rubocop_todo/lint/empty_block.yml

.rubocop_todo/performance/regexp_match.yml

.rubocop_todo/rspec/feature_category.yml

.rubocop_todo/rspec/named_subject.yml

.rubocop_todo/style/inline_disable_annotation.yml

.rubocop_todo/style/mutable_constant.yml

...ent/gitlab_flavored_markdown/specification_guide/index.md

glfm_specification/README.md

...cation/input/github_flavored_markdown/ghfm_spec_v_0.29.md

.../input/gitlab_flavored_markdown/glfm_example_metadata.yml

.../gitlab_flavored_markdown/glfm_example_normalizations.yml

...on/input/gitlab_flavored_markdown/glfm_example_status.yml

...nput/gitlab_flavored_markdown/glfm_internal_extensions.md

...t/gitlab_flavored_markdown/glfm_official_specification.md

...specification/output_example_snapshots/examples_index.yml

glfm_specification/output_example_snapshots/html.yml