Vinegar can be used on an occasional basis when doing the final stripping rinse of the cloth diapers to help remove any leftover detergent but you should avoid using Vinegar too much when cleaning cloth diapers.
Vinegar is acidic and could ruin the cloth diapers if used too much so as long as you use the Vinegar sparingly for stripping the cloth diapers then it's okay.
But you should use regular laundry detergent when washing cloth diapers to keep them from becoming ruined.