mailing recipients field limits how many groups can be selected

When creating a mailing, the mailing recipients group currently limits how many groups (or mailings) can be selected. It appears that the option in search preferences for "autocomplete results" is not only determining how many records appear in the search result dropdown at a time, but also limits how many options can be selected. It should not be doing that. We should also do a bit of investigation to see if that behavior is impacting other instances of the Select2 widget.