Flaky test: "replication_set_should_not_change_if_ring_did_not_change,_when_num_of_instance_per_zone_is_inconsistent"

[CharlieTLe]

Noticed build failure: https://github.com/cortexproject/cortex/actions/runs/12798522991/job/35682746078?pr=6511

--- FAIL: TestRing_Get_Consistency (488.91s)
    --- FAIL: TestRing_Get_Consistency/replication_set_should_not_change_if_ring_did_not_change,_when_num_of_instance_per_zone_is_inconsistent (61.47s)
        ring_test.go:735: 
            	Error Trace:	/__w/cortex/cortex/pkg/ring/ring_test.go:735
            	Error:      	"1" is not less than or equal to "0"
            	Test:       	TestRing_Get_Consistency/replication_set_should_not_change_if_ring_did_not_change,_when_num_of_instance_per_zone_is_inconsistent
FAIL
FAIL	github.com/cortexproject/cortex/pkg/ring	704.951s