Modernize common probes to use context manager

[voetberg]

Probes https://github.com/rucio/probes/blob/master/common/check_expired_locked_rules and https://github.com/rucio/probes/blob/master/common/check_obsolete_replicas don't use a context manager so they're inaccessible to Prometheus. They should be updated to use common.utils.PromotheusPusher