This was introduced with commit 9ab338d7b6 because the clipping of
fractionally scaled redraws caused glitches, it seems like this is no
longer needed nowadays, so let's remove it.
This should make obscured region culling work a bit better for
fractionally scaled framebuffers because because we overdraw a slightly
smaller region than the actually damaged one. We still do overdraw
though since the clipping region is stored using integers and thus
any non-integer values have to be extended to the bounding rect.
https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1113
8c52b431bb