Restore exit code for Java in metadata update script

Author: twcclegg

lib/github-actions-metadata-update.sh

@@ -85,7 +85,7 @@ FILES=$(getReleaseDelta google/libphonenumber "v${DEPLOYED_NUGET_TAG}" $UPSTREAM
 if echo $FILES | grep '\.java'
 then
    echo "has java files, automatic update not possible"
-   #exit 123
+   exit 123
 fi
 
 if echo $FILES | grep 'proto'