Remove flaky check from StateFlowStressTest.

There's no guarantee that any particular collector will ever encounter
a value emitted by a particular emitter. It's entirely possible for the
value to be overwritten by a different emitter before the collector gets
a chance to collect it. It's very, very unlikely for a collector to miss
the second half of all values emitted by a particular emitter, but it
is possible to happen and this causes the test to be flaky.

Author: chaoren

kotlinx-coroutines-core/jvm/test/flow/StateFlowStressTest.kt

@@ -63,10 +63,6 @@ class StateFlowStressTest : TestBase() {
         }
         emitters.cancelAndJoin()
         collectors.cancelAndJoin()
-        // make sure nothing hanged up
-        require(collected.all { c ->
-            c.withIndex().all { (emitter, current) -> current > emitted[emitter] / 2 }
-        })
     }
 
     @Test