textrender: Fix AYUV output.

Fix the check for whether the element is operating in ARGB mode. It
was incorrectly checking if the output format has an alpha channel,
which is true for both ARGB and AYUV, leading to the element
incorrectly outputting ARGB values into AYUV caps.

ext/pango/gsttextrender.c

@@ -341,7 +341,7 @@ gst_text_render_check_argb (GstTextRender * render)
       if (info == NULL)
         continue;
 
-      render->use_ARGB = GST_VIDEO_FORMAT_INFO_HAS_ALPHA (info);
+      render->use_ARGB = GST_VIDEO_FORMAT_INFO_IS_RGB (info);
     }
     gst_caps_unref (peer_caps);
   }