Add v1.min.io/tenant label to minio service

v6.x -> v7.x removed the v1.min.io/tenant label for the minio service

!3707 (merged)

https://github.com/minio/operator/compare/v6.0.4...v7.0.0#diff-23e0afc6450903ba4ce6cd4ce4d7d537a69251a712402a5ad98b805c5eaec63fL54

We use this label to discover the minio pods for monitoring. Without this label minio is not monitored

without the patch:

$ kubectl -n minio-monitoring describe svc minio 
 
Name:              minio
Namespace:         minio-monitoring
Labels:            <none>
Annotations:       <none>

with this patch:

$ kubectl -n minio-monitoring describe svc minio 
 
Name:              minio
Namespace:         minio-monitoring
Labels:            v1.min.io/tenant=monitoring
Annotations:       <none>

Related issue: #2142 (closed)