Yes, you can use the
admin.enableRichTextRelationship property. Set it to false for any collection you don't want to be able to link to.
Right now, rich text uploads offer a bit more granularity here, as you can specifically whitelist collections to be able to select from on a field-by-field basis. But in the future we should be able to add more granularity to do this with rich text relationships too. 👍