Update generate-terraform.sh

.ci/magic-modules/generate-terraform.sh

@@ -70,13 +70,13 @@ git config --global user.name "Modular Magician"
 
 git add -A
 
-# TODO: Remove this, this is just to see what the Magician does
+# This is useful for human debugging, but not necessary for the Magician.
 git status
 
-# go mod vendor is a very expensive operation.
-# If no changes, avoid running.
+# Only run `go mod vendor` if we see changes in this downstream repo, since it takes a while to run
 if [[ ! -z $(git status -s) ]]; then
   GO111MODULE=on go mod vendor
+  git add -A
 fi
 
 # Set the "author" to the commit's real author.