threading_support: delete the critical section

Although the CriticalSection itself doesnt need to be destroyed, there
may be debug data associated with it.  Plug a possible small leak.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@291536 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed