Make sure the avparser is used for VP9 rather than the Copy Packetizer

Fixes #11690 which didn't work with avcodec
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/packetizer/avparser.h

@@ -47,5 +47,5 @@ void ClosePacketizer( vlc_object_t * );
     set_category( CAT_SOUT )                            \
     set_subcategory( SUBCAT_SOUT_PACKETIZER )           \
     set_description( N_("avparser packetizer") )        \
-    set_capability( "packetizer", 1 )                   \
+    set_capability( "packetizer", 20 )                   \
     set_callbacks( OpenPacketizer, ClosePacketizer )