remove reference to glgsg.h

panda/src/x11display/x11GraphicsWindow.cxx

@@ -19,7 +19,6 @@
 #include "graphicsPipe.h"
 #include "keyboardButton.h"
 #include "mouseButton.h"
-#include "glgsg.h"
 #include "clockObject.h"
 #include "pStatTimer.h"
 #include "textEncoder.h"