Revert "[libc++] Add a test that uses the debug database from multiple threads"

This reverts r358591, which seems to have uncovered an actual bug and
causes the tsan CI to fail. We need to fix the bug and re-commit the
test.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@358593 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed