[libc++] Fixes an AIX CI failure.

The test now seems to pass so remove the XFAIL.

Author: mordante

libcxx/test/std/re/re.traits/transform.pass.cpp

@@ -8,7 +8,6 @@
 //
 // NetBSD does not support LC_COLLATE at the moment
 // XFAIL: netbsd
-// XFAIL: LIBCXX-AIX-FIXME
 
 // REQUIRES: locale.cs_CZ.ISO8859-2