Codegen: rm client files before regen

hack/update-codegen.sh

@@ -646,6 +646,12 @@ function codegen::clients() {
         done
     fi
 
+    git_grep -l --null \
+        -e '^// Code generated by client-gen. DO NOT EDIT.$' \
+        -- \
+        ':(glob)staging/src/k8s.io/client-go/**/*.go' \
+        | xargs -0 rm -f
+
     "${clientgen}" \
         --go-header-file "${BOILERPLATE_FILENAME}" \
         --output-base "${KUBE_ROOT}/vendor" \