Revise polkit messages again

I realized that these messages are a bit confusing, with
keep permissions and implications. We end up asking a
question about one ref, but then use the permission we optained
to operate on other refs. This will get a bit worse with
the new hints, so go back to more generic messages that
don't talk about the details. The ultimate goal here is
less messages, anyway.

Closes: #2384
Approved by: alexlarsson
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