Fix: [MacOS] screen looks blue-ish when using newer SDKs (#11207)

The define kCGBitmapByteOrder32Host changed (around SDK 12?)
into an enum, which means an old #ifndef was triggering,
overwriting the value to 0. Sadly, 0 means Order16Big, causing
RGBA to become GRAB, which results in strange colours.

As we no longer support PPC, drop that piece of code completely.

src/video/cocoa/cocoa_v.mm

@@ -64,13 +64,6 @@
  * Read http://developer.apple.com/releasenotes/Cocoa/Objective-C++.html for more information.
  */
 
-/* On some old versions of MAC OS this may not be defined.
- * Those versions generally only produce code for PPC. So it should be safe to
- * set this to 0. */
-#ifndef kCGBitmapByteOrder32Host
-#define kCGBitmapByteOrder32Host 0
-#endif
-
 bool _cocoa_video_started = false;
 static Palette _local_palette; ///< Current palette to use for drawing.