Replace whitespaces in wiki page attachments file names

What does this MR do?

CommonMark does not accept white spaces in URLs. This MR replace white spaces when we attach a file to a wiki page.

The commit that replaced RedCarpet to CommonMark is https://gitlab.com/gitlab-org/gitlab-ce/commit/5a7451c2f91e5ed7fa95f6abb5eaceaf220945cb

What are the relevant issue numbers?

Closes #51194 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides