Fix race on the LabelSet Counter #10667

Job	Run time
CodeQL	6m 50s
test	15m 44s
build	4m 2s
lint	4m 18s
integration-configs-db	2m 49s
integration (requires_docker)	7m 29s
integration (integration_alertmanager)	4m 8s
integration (integration_backward_compatibility)	10m 44s
integration (integration_memberlist)	7m 49s
integration (integration_querier)	15m 30s
integration (integration_ruler)	5m 39s
integration (integration_query_fuzz)	4m 39s
deploy_website	0s
deploy	0s
	1h 29m 41s

Provide feedback