Revert "CoreFoundation: add a workaround for Linux with the rebranch"

This reverts commit 67eb223.

Author: etcwilde

CoreFoundation/String.subproj/CFAttributedString.c

@@ -23,10 +23,6 @@
 @end
 #endif
 
-#if defined(__linux__)
-#pragma clang optimize off
-#endif
-
 struct __CFAttributedString {
     CFRuntimeBase base;
     CFStringRef string;