Log Message:
gtk4: update to 4.8.1.

Overview of Changes in 4.8.1, 16-09-2022
========================================

* Input:
 - Fix problems with input method interactions that caused
   dead keys not to work
 - Accept single-key compose sequences (these are used with
   some keyboard layouts)

* GtkColumnView:
 - Flip column order in right-to-left context

* GtkGridView:
 - Fix problems with rubberbanding

* GtkFileChooser:
 - Fix positioning of popovers in the places view
 - Make ~ and . keyboard shortcuts work again

* gsk:
 - Make glyph upload more similar to icons

* Make file transfer via portals work, this fixes file
  copy/paste and dnd in flatpaks