Use class template argument deduction for locks

src/test/core/Coroutine_test.cpp

@@ -52,7 +52,7 @@ public:
         void
         signal()
         {
-            std::lock_guard<std::mutex> lk(mutex_);
+            std::lock_guard lk(mutex_);
             signaled_ = true;
             cv_.notify_all();
         }

src/test/core/Workers_test.cpp

@@ -90,7 +90,7 @@ public:
     {
         void processTask(int instance) override
         {
-            std::lock_guard<std::mutex> lk{mut};
+            std::lock_guard lk{mut};
             if (--count == 0)
                 cv.notify_all();
         }