fix: add Plural annotation to match CRD manifest

Author: metacosm

operator-framework/src/test/java/io/javaoperatorsdk/operator/sample/subresource/SubResourceTestCustomResource.java

@@ -4,11 +4,13 @@
 import io.fabric8.kubernetes.client.CustomResource;
 import io.fabric8.kubernetes.model.annotation.Group;
 import io.fabric8.kubernetes.model.annotation.Kind;
+import io.fabric8.kubernetes.model.annotation.Plural;
 import io.fabric8.kubernetes.model.annotation.Version;
 
 @Group("sample.javaoperatorsdk")
 @Version("v1")
 @Kind("SubresourceSample")
+@Plural("subresourcesample")
 public class SubResourceTestCustomResource
     extends CustomResource<SubResourceTestCustomResourceSpec, SubResourceTestCustomResourceStatus>
     implements Namespaced {}