tmpfiles: exclude x11 lock files from time-based cleanup

tmpfiles: exclude x11 lock files from time-based cleanup

We need a removal rule for systems where /tmp is not on tmpfs,
so that if they crash, stale sockets will be removed during boot.
OTOH, at runtime, those lock files must never be removed.
But since the 'r!' rule uses '!', it only applies during boot. With
the rule inactive, the usual time-based cleanup for /tmp/ was also
applied to those files, causing them to be removed after 10 days.

Fixes #35182.