[libc++] Mark -fexperimental-library test as unsupported on another AppleClang

(cherry picked from commit 144cea2)

Author: ldionne

libcxx/test/libcxx/experimental/fexperimental-library.compile.pass.cpp

@@ -16,7 +16,7 @@
 // UNSUPPORTED: clang-13, clang-14
 
 // AppleClang does not support the -fexperimental-library flag yet
-// UNSUPPORTED: apple-clang-13
+// UNSUPPORTED: apple-clang-13, apple-clang-14.0
 
 // Clang on AIX currently pretends that it is Clang 15, even though it is not (as of writing
 // this, LLVM 15 hasn't even been branched yet).