Fixes #14815 - Fixed translation string

[snipe]

Fixes #14815 - we were using the wrong translation error string for deleting an undeleteable location.

[what-the-diff]

PR Summary

• Updated error message in LocationsController
  The file controlling how we manage locations had a small update. We improved the error message shown to users by linking it to a more appropriate translation key. This means, in the context of an error happening, our users will now see a more accurate notification.

• Enhanced error description in admin/locations' message file
  In the administrative side of our location management, a more detailed error message has been introduced. The update is through the assoc_users translation key. Our admins will now receive more specific error information, facilitating faster problem diagnosis and resolution.