Change Done column to Closed in issue boards

What does this MR do?

Changes Done column to Closed in issue boards.

Are there points in the code the reviewer needs to double check?

I'm not sure if the Done/Closed list should be available on empty issue boards (no list added yet).
I synced my fork with upstream and tried to check if Done list was presented in an empty issue boards.
In the master branch it wasn't there. In this branch it's not there either.
But on GitLab.com empty Done list is presented.

Is it a EE feature? Or am I missed something?

Why was this MR needed?

Closed list stores closed issues. Let's make things consistent!

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #29420 (closed)