qemu_command: Remove outdated comment

Signed-off-by: NMaciej Wolny <maciej.wolny@codethink.co.uk>
Reviewed-by: NJohn Ferlan <jferlan@redhat.com>

src/qemu/qemu_command.c

@@ -7630,9 +7630,6 @@ qemuBuildGraphicsSDLCommandLine(virQEMUDriverConfigPtr cfg ATTRIBUTE_UNUSED,
     virCommandAddEnvPassBlockSUID(cmd, "QEMU_AUDIO_DRV", NULL);
     virCommandAddEnvPassBlockSUID(cmd, "SDL_AUDIODRIVER", NULL);
 
-    /* New QEMU has this flag to let us explicitly ask for
-     * SDL graphics. This is better than relying on the
-     * default, since the default changes :-( */
     virCommandAddArg(cmd, "-sdl");
     return 0;
 }