testsuite: Avoid negative scales with gl renderer

The fix in 1c90bb522e was only for the ngl renderer,
so don't use the test with the gl renderer, until it is
fixed as well.

testsuite/gsk/meson.build

@@ -69,7 +69,7 @@ compare_render_tests = [
   'outset_shadow_rounded_top',
   'outset_shadow_simple',
   'scaled-cairo',
-  'scale-textures-negative',
+  'scale-textures-negative-ngl',
   'scale-up-down',
   'shadow-in-opacity',
   'texture-url',