plug: Remove size_allocate handler
plug: Remove size_allocate handler

Since windows can be intermediate containers this is somewhat redundant,
plus gtk_window_size_allocate() will do additional things like allocating
the popovers, which was mistakenly skipped by local plugs not chaining up.

https://bugzilla.gnome.org/show_bug.cgi?id=747553

jadahl/gtk,Adamovskiy/gtk,jadahl/gtk,alexlarsson/gtk,alexlarsson/gtk,Adamovskiy/gtk,grubersjoe/adwaita,jigpu/gtk,jadahl/gtk,grubersjoe/adwaita,alexlarsson/gtk,chergert/gtk,Adamovskiy/gtk,jigpu/gtk,jigpu/gtk,jadahl/gtk,chergert/gtk,chergert/gtk,Adamovskiy/gtk,grubersjoe/adwaita,grubersjoe/adwaita,alexlarsson/gtk,jadahl/gtk,grubersjoe/adwaita,chergert/gtk,davidgumberg/gtk,Adamovskiy/gtk,chergert/gtk,alexlarsson/gtk,Adamovskiy/gtk,chergert/gtk,jadahl/gtk,Adamovskiy/gtk,davidgumberg/gtk,alexlarsson/gtk,jadahl/gtk,davidgumberg/gtk,jigpu/gtk,jigpu/gtk,grubersjoe/adwaita,chergert/gtk,davidgumberg/gtk,jigpu/gtk,davidgumberg/gtk,jadahl/gtk,grubersjoe/adwaita,davidgumberg/gtk,grubersjoe/adwaita,Adamovskiy/gtk,jigpu/gtk,alexlarsson/gtk,jigpu/gtk,davidgumberg/gtk,chergert/gtk,alexlarsson/gtk,davidgumberg/gtk