[babl] meson: add transparent_symmetry test

[Øyvind "pippin" Kolås <ok src gnome org>]

commit 20c9630ed82b6ea338806a8a402ad87f532de67f
Author: Øyvind Kolås <pippin gimp org>
Date:   Thu Jun 13 17:12:36 2019 +0200

    meson: add transparent_symmetry test

 tests/meson.build | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/tests/meson.build b/tests/meson.build
index b4ca78c..06ee6b7 100644
--- a/tests/meson.build
+++ b/tests/meson.build
@@ -21,6 +21,7 @@ test_names = [
   'sanity',
   'srgb_to_lab_u8',
   'transparent',
+  'transparent_symmetry',
   'types',
 ]
 if platform_unix