Remove sleep workaround in thread pool.

Not required after the race condition in bionic has been fixed.
Bug: 11693195

Change-Id: Ib27ff79d86caa50676b40a0acd3cab071e65779f
diff --git a/runtime/thread_pool.cc b/runtime/thread_pool.cc
index 67fcd58..aca0561 100644
--- a/runtime/thread_pool.cc
+++ b/runtime/thread_pool.cc
@@ -43,8 +43,6 @@
 
 ThreadPoolWorker::~ThreadPoolWorker() {
   CHECK_PTHREAD_CALL(pthread_join, (pthread_, NULL), "thread pool worker shutdown");
-  // TODO: Delete this when race condition in pthread_join is fixed.
-  usleep(500);
 }
 
 void ThreadPoolWorker::Run() {