changes it back into WithSubstreamsSupport

Author: eaba

src/core/Akka.Streams.Tests/Dsl/FlowSplitWhenSpec.cs

@@ -54,7 +54,7 @@ public StreamPuppet(IPublisher<int> p, TestKitBase kit)
 
             public async Task ExpectNextAsync(int element) => await _probe.ExpectNextAsync(element);
 
-            public async Task ExpectNoMsgAsync(TimeSpan max) => await _probe.ExpectNoMsgAsync(max);
+            public void ExpectNoMsg(TimeSpan max) => _probe.ExpectNoMsg(max);
 
             public async Task ExpectCompleteAsync() => await _probe.ExpectCompleteAsync();
 
@@ -93,7 +93,7 @@ await this.AssertAllStagesStoppedAsync(() => {
                     {                                                                                 
                         var s1 = new StreamPuppet(getSubFlow()                                                                                     
                             .RunWith(Sink.AsPublisher<int>(false), Materializer), this);                                                                                 
-                        await masterSubscriber.ExpectNoMsgAsync(TimeSpan.FromMilliseconds(100));                                                                                 
+                        masterSubscriber.ExpectNoMsg(TimeSpan.FromMilliseconds(100));                                                                                 
                         s1.Request(2);                                                                                 
                         await s1.ExpectNextAsync(1);                                                                                 
                         await s1.ExpectNextAsync(2);                                                                                 
@@ -102,11 +102,11 @@ await this.AssertAllStagesStoppedAsync(() => {
 
                         var s2 = new StreamPuppet(getSubFlow()                                                                                     
                             .RunWith(Sink.AsPublisher<int>(false), Materializer), this);                                                                                 
-                        await masterSubscriber.ExpectNoMsgAsync(TimeSpan.FromMilliseconds(100));
+                        masterSubscriber.ExpectNoMsg(TimeSpan.FromMilliseconds(100));
 
                         s2.Request(1);                                                                                 
-                        await s2.ExpectNextAsync(3);                                                                                 
-                        await s2.ExpectNoMsgAsync(TimeSpan.FromMilliseconds(100));
+                        await s2.ExpectNextAsync(3);
+                        s2.ExpectNoMsg(TimeSpan.FromMilliseconds(100));
 
                         s2.Request(1);                                                                                 
                         await s2.ExpectNextAsync(4);