CMake: don't blacklist TARGET_OS_SIMULATOR for Metal configuration

https://github.com/libsdl-org/SDL/commit/7fa5e95b6284f2cc7855022c9f0c2b086dcee43f enabled it.

CMakeLists.txt

@@ -1903,7 +1903,7 @@ elseif(APPLE)
         #import <Metal/Metal.h>
         #import <QuartzCore/CAMetalLayer.h>
 
-        #if TARGET_OS_SIMULATOR || (!TARGET_CPU_X86_64 && !TARGET_CPU_ARM64)
+        #if (!TARGET_CPU_X86_64 && !TARGET_CPU_ARM64)
         #error Metal doesn't work on this configuration
         #endif
         int main()