cloud-provider-gcp add current maintainers as OWNERS

See current cloud-provider-gcp maintainers at https://github.com/kubernetes/org/blob/main/config/kubernetes/provider-gcp/teams.yaml

Author: mmamczur

config/jobs/kubernetes/cloud-provider-gcp/OWNERS

@@ -4,10 +4,14 @@ reviewers:
 - mikedanese
 - jpbetz
 - jprzychodzen
+- mmamczur
+- YifeiZhuang
 approvers:
 - mikedanese
 - jpbetz
 - jprzychodzen
+- mmamczur
+- YifeiZhuang
 emeritus_approvers:
 - amwat
 labels: