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

Partially reverts 04dbb634.

This test requires 9be8f8b3
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