hack/*.sh: re-add staging dirs to verify+update scripts

hack/update-gofmt.sh

@@ -34,11 +34,10 @@ find_files() {
         -o -wholename './_output' \
         -o -wholename './_gopath' \
         -o -wholename './release' \
-        -o -wholename './staging' \
         -o -wholename './target' \
         -o -wholename '*/third_party/*' \
         -o -wholename '*/vendor/*' \
-        -o -wholename './staging' \
+        -o -wholename './staging/src/k8s.io/client-go/*vendor/*' \
       \) -prune \
     \) -name '*.go'
 }