disables the shortcut to the issue boards when issues are disabled

What does this MR do?

It disables the shortcut g b (go to issue boards) for a project that has issues disabled.

In addition, it also fixes the following:

• the shortcut i (create new issue) is also disabled if issues are disabled
• going to the issues board renders a 404 when issues are disabled (similar to issues)
• the assertion that a shortcut is disabled is changed, cause it was prone to false positives (asserting that a user is not at the destination, whereas the assertion should be that the user is not redirected, i.e. stays on the same page)

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

Why was this MR needed?

It should not possible to go the issue boards when issues are not enabled for a project.

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
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered

What are the relevant issue numbers?

Closes #41244 (closed)