Share suggestions cannot be hidden or changed. If you have a picture you want to share and click the share button, two bars show up, one "send in Google photos" and the other to "share to apps". The first bar has people suggestions. These suggestions seem completely random and, so useless to the user. The worst part is that if you want a contact to never show in the suggestions, you must delete them from your contacts. No Google photos, I do not want to delete my contact.