More detailed branch delete message (#22696)

Fix #22624 . Message explains that deleted branch can only be restored for a short time period.

options/locale/locale_en-US.ini

@@ -2380,7 +2380,7 @@ branch.already_exists = A branch named "%s" already exists.
 branch.delete_head = Delete
 branch.delete = Delete Branch "%s"
 branch.delete_html = Delete Branch
-branch.delete_desc = Deleting a branch is permanent. It <strong>CANNOT</strong> be undone. Continue?
+branch.delete_desc = Deleting a branch is permanent. Although the deleted branch may exist for a short time before cleaning up, in most cases it CANNOT be undone. Continue?
 branch.deletion_success = Branch "%s" has been deleted.
 branch.deletion_failed = Failed to delete branch "%s".
 branch.delete_branch_has_new_commits = Branch "%s" cannot be deleted because new commits have been added after merging.