shiny/driver/gldriver: disable forced OpenGL acceleration on macOS

Fixes golang/go#19191

Change-Id: I932119963f5ea46166d741c9427a6941ed700ee5
Reviewed-on: https://go-review.googlesource.com/44379
Reviewed-by: Nigel Tao <nigeltao@golang.org>
diff --git a/shiny/driver/gldriver/cocoa.m b/shiny/driver/gldriver/cocoa.m
index e8e863e..1e96e3f 100644
--- a/shiny/driver/gldriver/cocoa.m
+++ b/shiny/driver/gldriver/cocoa.m
@@ -284,7 +284,6 @@
 			NSOpenGLPFAColorSize,     24,
 			NSOpenGLPFAAlphaSize,     8,
 			NSOpenGLPFADepthSize,     16,
-			NSOpenGLPFAAccelerated,
 			NSOpenGLPFADoubleBuffer,
 			NSOpenGLPFAAllowOfflineRenderers,
 			0