fix: PR checks failing because of google/cloud/gkehub/policycontroller/v1beta dependency missing

Adding proto_path, google/cloud/gkehub/policycontroller/v1beta, to gkehub in the generation_config.yaml.
google/cloud/gkehub/policycontroller/v1beta was added as a dependency of
google/cloud/gkehub/v1beta in googleapis/googleapis@8c534a5

Author: jinseopkim0

generation_config.yaml

@@ -1054,6 +1054,7 @@ libraries:
   - proto_path: google/cloud/gkehub/v1alpha
   - proto_path: google/cloud/gkehub/v1beta
   - proto_path: google/cloud/gkehub/v1beta1
+  - proto_path: google/cloud/gkehub/policycontroller/v1beta
   - proto_path: google/cloud/gkehub/servicemesh/v1beta
 
 - api_shortname: containeranalysis