No devices available: regression caused by new restrictions in systemd unit

After 2fd86624, I get:

$ fprintd-verify
list_devices failed: No devices available

My device is 06cb:00bd (Synaptics, Inc. Prometheus MIS Touch Fingerprint Reader)

If I remove ProtectClock=yes from the unit file and restart the service, it works correctly:

$ fprintd-verify
Using device /net/reactivated/Fprint/Device/0
Listing enrolled fingers:
 - #0: right-index-finger
Verify result: verify-match (done)

According to Timothy Gu, the TasksMax=1 restriction can also cause issues.