Document need to rerun codegen when changing _example key (#8196)
Document need to rerun codegen when changing _example key (#8196)

* Document need to rerun codegen when changing _example

* format

Co-authored-by: Matt Moore <866b498749d560dfd4b9805e44d1fa0b8bc948c7@vmware.com>

Co-authored-by: Matt Moore <866b498749d560dfd4b9805e44d1fa0b8bc948c7@vmware.com>
knative/serving,knative/serving