TEST-60-MOUNT-RATELIMIT sometimes fails as it cannot see the 'left rate limit'
message in the journal. Tests relying on specific log messages are often flaky,
as the journal is lossy.
Change the test case to check for the desired outcome instead, as that also
catches regressions, without being over reliant on the journal.
Fixes https://github.com/systemd/systemd/issues/32712