calls-best-match: AdwAvatar API changes

https://gnome.pages.gitlab.gnome.org/libadwaita/doc/main/migrating-libhandy-1-4-to-libadwaita.html#adapt-to-adwavatar-api-changes

This is *not* ideal, since it relies on Folks returning a GFileIcon
internally, and it's also blocking. However, better to use something
simple that compiles and works to begin with.

Part-of: <https://gitlab.gnome.org/GNOME/calls/-/merge_requests/714>

src/calls-call-record-row.c

@@ -357,7 +357,7 @@ setup_contact (CallsCallRecordRow *self)
                           G_BINDING_SYNC_CREATE);
 
   g_object_bind_property (self->contact, "avatar",
-                          self->avatar, "loadable-icon",
+                          self->avatar, "custom-image",
                           G_BINDING_SYNC_CREATE);
 
 }