Folks.Individual: don't use is-writeable in change_avatar
Folks.Individual: don't use is-writeable in change_avatar

This is a follow-up for commit 96539acd, using PersonaStore.is_writeable
is deprecated in favour of checking Persona.writeable_properties

renatofilho/folks2,renatofilho/folks2,GNOME/folks,pwithnall/folks,GNOME/folks,renatofilho/folks2,renatofilho/folks,pwithnall/folks,renatofilho/folks,renatofilho/folks,renatofilho/folks,GNOME/folks,pwithnall/folks,renatofilho/folks2