The right to force merge is uses the wrong predicate and
applies to instance admins:
ctx.user.IsAdmin
It must apply to repository admins and use the following predicate:
ctx.userPerm.IsAdmin()
This regression is from the ApplyToAdmins implementation in
79b7089360.
Fixes: https://codeberg.org/forgejo/forgejo/issues/3780
(cherry picked from commit 09f3518069)
