ci: Install GTK4 from brew on macOS

QuLogic · QuLogic · commit e46342eea0c3 · 2023-08-26T00:12:24.000-04:00
We try to install PyGObject everywhere, but this doesn't work because
GTK itself is not available from PyPI.
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
@@ -144,7 +144,7 @@ jobs:
           macOS)
             brew install ccache
             brew tap homebrew/cask-fonts
-            brew install font-noto-sans-cjk
+            brew install font-noto-sans-cjk gobject-introspection gtk4
             ;;
           esac
 
