[Concurrency] Relax assertions in startSynchronously test

[ktoso]

resolves rdar://145735542

We observed the following ordering on linux:

            35: inside startSynchronously [thread:139847144564480] @ :266 
>>>> call the actor
            36: inside startSynchronously, call rec.sync() [thread:139847144564480] @ :274 
            37: Recipient/sync(syncTaskThreadID:) Current actor thread id = 139847385605888 @ :230 
            38: inside startSynchronously, call rec.sync() done [thread:139847144564480] @ :279 
>>>> it was a default actor and completed the call on the calling
            39: Inner thread id = 139847144564480 
            40: Current thread id = 139847144564480 
            41: NOTICE: Task resumed on same thread as it entered the synchronous task! 
            42: inside startSynchronously, call rec.async() [thread:139847144564480] @ :292 
            43: Recipient/async(syncTaskThreadID:) Current actor thread id = 139847385605888 @ :242 
            44: inside startSynchronously, call rec.async() done [thread:139847144564480] @ :297 
            45: Inner thread id = 139847144564480 
            46: Current thread id = 139847144564480 
            47: NOTICE: Task resumed on same thread as it entered the synchronous task! 
            48: inside startSynchronously, done [thread:139847144564480] @ :308 
            49: after startSynchronously [thread:139847144564480] @ :312 

I will actually take some more time to investigate this

[ktoso]

@swift-ci please smoke test