Fix typo

core/mem/alloc.odin

@@ -57,7 +57,7 @@ DEFAULT_ALIGNMENT :: 2*align_of(rawptr)
 
 DEFAULT_PAGE_SIZE ::
 	64 * 1024 when ODIN_ARCH == .wasm32 || ODIN_ARCH == .wasm64 else
-	16 * 1024 when ODIN_OS == .darwin && ODIN_ARCH == .arm64 else
+	16 * 1024 when ODIN_OS == .Darwin && ODIN_ARCH == .arm64 else
 	4 * 1024
 
 alloc :: proc(size: int, alignment: int = DEFAULT_ALIGNMENT, allocator := context.allocator, loc := #caller_location) -> rawptr {