chore: update .github/trusted-contribution.yml

Author: cloud-foundation-bot

.github/trusted-contribution.yml

@@ -12,6 +12,9 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+# NOTE: This file is automatically generated from:
+# https://github.com/GoogleCloudPlatform/cloud-foundation-toolkit/blob/master/infra/terraform/test-org/github
+
 annotations:
   - type: comment
     text: "/gcbrun"