Revert "libutils: Fix race condition in Thread::requestExitAndWait()"

This change turned out to be unnecessary

This reverts commit 4a7f412e1d932f46f6adf079df4d9ee7279bd795.
diff --git a/libs/utils/Threads.cpp b/libs/utils/Threads.cpp
index 00d009b..ad9a94f 100644
--- a/libs/utils/Threads.cpp
+++ b/libs/utils/Threads.cpp
@@ -799,9 +799,6 @@
 
 status_t Thread::requestExitAndWait()
 {
-    // hold a reference so mThreadExitedCondition is not destroyed before wait() returns
-    sp<Thread> strong(mHoldSelf);
-
     if (mThread == getThreadId()) {
         LOGW(
         "Thread (this=%p): don't call waitForExit() from this "