rest: simplify PatchewPermission
rest: simplify PatchewPermission

Because has_permission is always invoked before has_object_permission,
and both must pass for the request to be allowed, it is not necessary
to check obj.project.maintained_by for messages.

Signed-off-by: Paolo Bonzini <69d3ebcf5ee4e7f05a50dc23cd96655b730804b4@redhat.com>

patchew-project/patchew,patchew-project/patchew,patchew-project/patchew,patchew-project/patchew