Fix layout of wxStaticText, and possibly other controls.

Fix layout of wxStaticText, and possibly other controls.
GtkLabel perversely does not use its actual size to do layout, but will use its
size request. So restore calling gtk_widget_set_size_request() for all widgets,
which was removed in r71465. See #14374

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@71644 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775