Reduce log verbosity for the gc service (#1392)

If the GC service is not authorixed to list some particular types, it
emits a message "cannot list resource" that may be misleading as it does
not impact the behavior of the GC service. This commit set the log
verbosity to 3 so it is not shown by default, but can be enabled
eventually for troubleshooting

pkg/services/gc/gc.go

@@ -117,7 +117,7 @@ func (gc *GC) Run(
 		items, err := dc.Resource(resources[r].GroupVersionResource()).Namespace("").List(ctx, lo)
 		if err != nil {
 			if k8serr.IsForbidden(err) {
-				l.Info(
+				l.V(3).Info(
 					"cannot list resource",
 					"reason", err.Error(),
 					"gvk", resources[r].GroupVersionKind(),