Include dotfiles when matching the .markdownlint folder

What does this MR do and why?

Fixes https://gitlab.com/gitlab-org/gitlab/-/jobs/6265338577#L9523:

Failures:
  1) .gitlab/ci/rules.gitlab-ci.yml patterns missed matched files does not miss files to match
     Failure/Error: expect(all_files - all_matching_files.to_a).to be_empty
       expected `["doc/.markdownlint/.markdownlint-cli2.yaml"].empty?` to be truthy, got false
     # ./spec/dot_gitlab_ci/rules_spec.rb:188:in `block (4 levels) in <main>'
     # ./spec/spec_helper.rb:436:in `block (3 levels) in <top (required)>'
     # ./spec/support/sidekiq_middleware.rb:9:in `with_sidekiq_server_middleware'
     # ./spec/spec_helper.rb:427:in `block (2 levels) in <top (required)>'
     # ./spec/spec_helper.rb:423:in `block (3 levels) in <top (required)>'
     # ./lib/gitlab/application_context.rb:68:in `with_raw_context'
     # ./spec/spec_helper.rb:423:in `block (2 levels) in <top (required)>'
     # ./spec/spec_helper.rb:270:in `block (2 levels) in <top (required)>'
     # ./spec/support/system_exit_detected.rb:7:in `block (2 levels) in <main>'
     # ./spec/support/fast_quarantine.rb:22:in `block (2 levels) in <main>'
     # ./spec/support/database/prevent_cross_joins.rb:106:in `block (3 levels) in <main>'
     # ./spec/support/database/prevent_cross_joins.rb:60:in `with_cross_joins_prevented'
     # ./spec/support/database/prevent_cross_joins.rb:106:in `block (2 levels) in <main>'

Validate locally

touch doc/.markdownlint/.markdownlint-cli2.yaml
irb

irb(main):001> Dir.glob('doc/.{markdownlint,vale}/**/*').include?('doc/.markdownlint/.markdownlint-cli2.yaml')
=> false
irb(main):002> Dir.glob('doc/.{markdownlint,vale}/**/*', File::FNM_DOTMATCH).include?('doc/.markdownlint/.markdownlint-cli2.yaml')
=> true

MR acceptance checklist

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