monitoring: fix MTU Mismatch alert rule and expr

monitoring: fix MTU Mismatch alert rule and expr

Fixes: https://tracker.ceph.com/issues/73290
Signed-off-by: Aashish Sharma <aasharma@redhat.com>
(cherry picked from commit bee24dec441b9e6b263e4498c2ab333b0a60a52d)

Conflicts:
	monitoring/ceph-mixin/prometheus_alerts.yml
	monitoring/ceph-mixin/tests_alerts/test_alerts.yml
	src/pybind/mgr/dashboard/frontend/src/app/ceph/cluster/prometheus/active-alert-list/active-alert-list.component.html
	src/pybind/mgr/dashboard/frontend/src/app/ceph/cluster/prometheus/active-alert-list/active-alert-list.component.ts
	src/pybind/mgr/dashboard/frontend/src/app/shared/datatable/table-key-value/table-key-value.component.scss