coroutines, testsuite: Enable a test.

This just enables a test that can now be run since we've
resolved the PRs blocking it.

2020-04-25  Iain Sandoe  <iain@sandoe.co.uk>

	* g++.dg/coroutines/torture/co-ret-16-simple-control-flow.C:
	Enable test.

gcc/testsuite/ChangeLog

+2020-04-25  Iain Sandoe  <iain@sandoe.co.uk>
+
+	* g++.dg/coroutines/torture/co-ret-16-simple-control-flow.C:
+	Enable test.
+
 2020-04-25  Patrick Palka  <ppalka@redhat.com>
 
 	* g++.dg/concepts/diagnostic11.C: New test.

gcc/testsuite/g++.dg/coroutines/torture/co-ret-16-simple-control-flow.C

-#if 0
-//  { d g-do run }
+//  { dg-do run }
 
 // Test returning an int.
 // We will use the promise to contain this to avoid having to include
@@ -46,4 +45,3 @@ int main ()
   PRINT ("main: returning");
   return 0;
 }
-#endif