fix: test: Drop a redundant racy check in fetchlimit test

This particular `fetchlimit` failure has been happening quite often since https://gitlab.isc.org/isc-projects/bind9/-/merge_requests/12124 removed the test re-runs with `flaky` (after fixing other instabilities inside the test).

Example failure: https://gitlab.isc.org/isc-projects/bind9/-/jobs/7780648

Merge branch 'nicki/fix-fetchlimit-recovery-quota-flaky' into 'main'

See merge request isc-projects/bind9!12393