Renders 404 if given project is not readable by the user on TODOS dashboard

Further explained on #33303 (closed), this MR prevents an user to see unauthorized project names on TODOS page.

Passing an unauthorized project id renders a 404 right away.

• 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](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
• ~~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 #33303 (closed)