Selected items limit shouldn't be displayed with multiple false.

Steps:

1. Edit UDW configuration in universal_discovery_widget.yml.
2. Set selected_items_limit in default: section to e.g. 3.
3. Set multiple in e.g. richtext_embed: section to false.
4. Reload cache.
5. Go to e.g. an article and in e.g. body click "+" form the richtext toolbar and choose "Embed".
6. Try selecting some (valid) content items.
7. Notice at the bottom of UDW next to "Confirmed items" the "Limit N max" is displayed.

Remarks: Recording attached.