[lsan][test] Disable many_tls_keys_pthread.cpp on AArch64

Partially reverts 04dbb63.

This test requires 9be8f8b
which is/has been reverted a few times but this test was
left enabled.

Currently that change is reverted and this test is failing:
http://lab.llvm.org:8011/#/builders/7/builds/2327

Author: DavidSpickett

compiler-rt/test/lsan/TestCases/many_tls_keys_pthread.cpp

@@ -7,7 +7,7 @@
 
 // On glibc, this requires the range returned by GetTLS to include
 // specific_1stblock and specific in `struct pthread`.
-// UNSUPPORTED: arm-linux, armhf-linux
+// UNSUPPORTED: arm-linux, armhf-linux, aarch64
 
 // TSD on NetBSD does not use TLS
 // UNSUPPORTED: netbsd