message dialogs - remove extraneous padding
message dialogs - remove extraneous padding

Removes unnecessary padding above message dialog headings. This
makes the dialogs look much more balanced.

https://bugzilla.gnome.org/show_bug.cgi?id=732857

https://bugzilla.gnome.org/show_bug.cgi?id=732882

davidgumberg/gtk,chergert/gtk,ahodesuka/gtk,jadahl/gtk,jessevdk/gtk,Lyude/gtk-,ahodesuka/gtk,jigpu/gtk,chergert/gtk,jessevdk/gtk,ahodesuka/gtk,grubersjoe/adwaita,davidgumberg/gtk,jigpu/gtk,jigpu/gtk,Lyude/gtk-,Adamovskiy/gtk,grubersjoe/adwaita,jadahl/gtk,alexlarsson/gtk,chergert/gtk,jigpu/gtk,davidgumberg/gtk,davidgumberg/gtk,jigpu/gtk,Adamovskiy/gtk,Adamovskiy/gtk,ahodesuka/gtk,alexlarsson/gtk,jessevdk/gtk,alexlarsson/gtk,davidgumberg/gtk,ahodesuka/gtk,davidgumberg/gtk,jessevdk/gtk,jadahl/gtk,alexlarsson/gtk,chergert/gtk,Lyude/gtk-,jessevdk/gtk,Lyude/gtk-,jessevdk/gtk,jigpu/gtk,jessevdk/gtk,Adamovskiy/gtk,chergert/gtk,Adamovskiy/gtk,jigpu/gtk,Lyude/gtk-,alexlarsson/gtk,jadahl/gtk,grubersjoe/adwaita,chergert/gtk,Lyude/gtk-,jigpu/gtk,grubersjoe/adwaita,jadahl/gtk,alexlarsson/gtk,chergert/gtk,jadahl/gtk,ahodesuka/gtk,chergert/gtk,Adamovskiy/gtk,grubersjoe/adwaita,jadahl/gtk,grubersjoe/adwaita,Lyude/gtk-,ahodesuka/gtk,Adamovskiy/gtk,alexlarsson/gtk,jadahl/gtk,davidgumberg/gtk,Adamovskiy/gtk,alexlarsson/gtk,grubersjoe/adwaita,davidgumberg/gtk,ahodesuka/gtk,grubersjoe/adwaita,Lyude/gtk-