Fix for #931

Seems like the synchronised was there for an older approach to rendering. Made redundant by the BufferStrategy in 2015. 

Now it causes issues on windows if you resize the window too quickly

core/src/processing/awt/PSurfaceAWT.java

@@ -227,7 +227,7 @@ public class PSurfaceAWT extends PSurfaceNone {
   }
 
 
-  synchronized protected void render() {
+  protected void render() {
     if (canvas.isDisplayable() &&
         graphics.image != null) {
       if (canvas.getBufferStrategy() == null) {