upnp: Use the default maximum content length of 16k.

Setting libupnp's maximum content length to zero makes it unable to
fetch any didl instead of the probably expected unlimited behavior.

modules/services_discovery/upnp.cpp

@@ -136,14 +136,6 @@ static int Open( vlc_object_t *p_this )
         return VLC_EGENERIC;
     }
 
-    i_res = UpnpSetMaxContentLength( 0 );
-    if( i_res != UPNP_E_SUCCESS )
-    {
-        msg_Err( p_sd, "Failed to set maximum content length: %s", UpnpGetErrorMessage( i_res ) );
-        Close( (vlc_object_t*) p_sd );
-        return VLC_EGENERIC;
-    }
-
     return VLC_SUCCESS;
 }