Hi,
I'm afraid a FeedItem can include only one AdGroupId in the AdGroupTargeting attribute. If you would like to use a FeedItem for multiple AdGroups, you'll need to clear the AdGroupTargeting and use an AdGroupFeed to associate this Feed to multiple AdGroups with the appropriate matchingFunction to select which FeedItem may serve. Please see this guide for more details on matching functions.
Regards,
Shwetha, AdWords API Team.