Use std::condition_variable in InputDispatcher

To complete the thread safety annotation work, switch over the usage of
AutoMutex to std::mutex.

Bug: 123097103
Test: interact with booted device
Change-Id: I722acd97c4cab285b0439f3c5d173c814936bce0
diff --git a/services/inputflinger/BlockingQueue.h b/services/inputflinger/BlockingQueue.h
index 4b16027..db9f26e 100644
--- a/services/inputflinger/BlockingQueue.h
+++ b/services/inputflinger/BlockingQueue.h
@@ -43,7 +43,7 @@
      * Blocks execution while queue is empty.
      */
     T pop() {
-        std::unique_lock<std::mutex> lock(mLock);
+        std::unique_lock lock(mLock);
         android::base::ScopedLockAssertion assumeLock(mLock);
         mHasElements.wait(lock, [this]{
                 android::base::ScopedLockAssertion assumeLock(mLock);