mgr/dashboard: fix flaky promql query test

mgr/dashboard: fix flaky promql query test

There is a test collision in "promql-query-test" test suite because two different IOPS panels with the same title and legend labels (Read, Write) are present, and the test framework is not able to distinguish between them.
There are two panels with the same title IOPS and legends Read / Write, but different expressions:\
1. ceph-application-overview.json
2. ceph-cluster-advanced.json

Fixes: https://tracker.ceph.com/issues/71318
Signed-off-by: Aashish Sharma <aasharma@redhat.com>