Don't expand notifications that pop up over the pointer

Don't expand notifications that pop up over the pointer

Expanding notifications automatically just because they popped up where
the pointer is positioned distracts the user. It can also lead to a behavior
that is surprising to the user by, for example, making the user's input
switch to the notification's text entry box.

It is possible to expand a notification that popped up over the pointer
by mousing away from it and then mousing back in immediately.

https://bugzilla.gnome.org/show_bug.cgi?id=617209