Revert "lib/video: set "video" prop to true when changing video tracks"

This reverts commit 3add8370.

This commit was incomplete (missing audio/spu support) and is now done in vlc
core. See 8bc1b9ff8747be1b87730bea14a1b3778aed0bd6.

lib/video.c

@@ -639,8 +639,6 @@ int libvlc_video_set_track( libvlc_media_player_t *p_mi, int i_track )
     {
         if( i_track == val_list.p_list->p_values[i].i_int )
         {
-            if( var_SetBool( p_input_thread, "video", true ) < 0)
-                break;
             if( var_SetInteger( p_input_thread, "video-es", i_track ) < 0 )
                 break;
             i_ret = 0;