Ignore test failures in GTK

It seems to incorrectly set the initial size, but that is fixed in F43,
so this is only done for F42 here.

[skip changelog]

0005-Partially-revert-TST-Fix-minor-issues-in-interactive.patch

@@ -20,7 +20,7 @@ index 4e3c1bbc2b..903ae87cbb 100644
      fig.savefig(result_after, format='png')
  
 -    assert result.getvalue() == result_after.getvalue()
-+    if 'qt' not in backend and 'wx' not in backend:
++    if 'qt' not in backend and 'wx' not in backend and 'gtk4' not in backend:
 +        # FIXME: This should be enabled everywhere once Qt5 is fixed on macOS
 +        # to not resize incorrectly.
 +        assert result.getvalue() == result_after.getvalue()