Handle escaping special characters in the gollum filter

What does this MR do and why?

https://gitlab.com/gitlab-org/ruby/gems/gitlab-glfm-markdown 0.0.21 fixes this - upgrade to the new gem

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

How to set up and validate locally

1. go into a project and create a wiki page with the title this [and] that

2. in the comment of an issue submit the markdown

   [[this \[and\] that]]

3. Clicking the link in the comment should take you to the wiki page.

Related to #452070