Incorrect branch coverage async pattern for targetframework net472 (#1169)

Incorrect branch coverage async pattern for targetframework

test/coverlet.tests.projectsample.netframework/AsyncAwaitStateMachineNetFramework.cs

@@ -0,0 +1,12 @@
+using System.Threading.Tasks;
+
+namespace coverlet.tests.projectsample.netframework
+{
+    public class AsyncAwaitStateMachineNetFramework
+    {
+        public async Task AsyncAwait()
+        {
+            await Task.CompletedTask;
+        }
+    }
+}