StreamObserverTest.maxActiveStreamsViolationError test failure

https://github.com/apple/servicetalk/pull/1258/checks?check_run_id=1531757582

```
Wanted but not invoked:
clientReadObserver.readCancelled();
-> at io.servicetalk.http.netty.StreamObserverTest.maxActiveStreamsViolationError(StreamObserverTest.java:169)

However, there was exactly 1 interaction with this mock:
clientReadObserver.requestedToRead(1L);
-> at io.servicetalk.transport.api.CatchAllTransportObserver$CatchAllReadObserver.lambda$requestedToRead$0(CatchAllTransportObserver.java:203)

at io.servicetalk.http.netty.StreamObserverTest.maxActiveStreamsViolationError(StreamObserverTest.java:169)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
at io.servicetalk.concurrent.internal.ServiceTalkTestTimeout$TimeoutStatement$CallableStatement.call(ServiceTalkTestTimeout.java:171)
at io.servicetalk.concurrent.internal.ServiceTalkTestTimeout$TimeoutStatement$CallableStatement.call(ServiceTalkTestTimeout.java:163)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
```

Start with StreamObserverTest.maxActiveStreamsViolationError at StreamObserverTest.java:169 and reproduce the failure from the linked check. Read CatchAllTransportObserver.java around CatchAllReadObserver.requestedToRead and trace the observer interaction. Done means the test's expected interaction matches the implemented behavior and the test passes.

Written by the indexing model from the issue text.