test(core): increase delta_time for flaky test (#34982)

This regularly flaked

libs/core/tests/unit_tests/tracers/test_memory_stream.py

@@ -102,15 +102,12 @@ async def test_queue_for_streaming_via_sync_call() -> None:
 
     for item in items:
         delta_time = item["receive_time"] - item["produce_time"]
-        # Allow a generous 10ms of delay
-        # The test is meant to verify that the producer and consumer are running in
-        # parallel despite the fact that the producer is running from another thread.
-        # abs_tol is used to allow for some delay in the producer and consumer
-        # due to overhead.
-        # To verify that the producer and consumer are running in parallel, we
-        # expect the delta_time to be smaller than the sleep delay in the producer
-        # * # of items = 30 ms
-        assert math.isclose(delta_time, 0, abs_tol=0.020) is True, (
+        # The test verifies that the producer and consumer are running in parallel
+        # despite the producer running from another thread via asyncio.to_thread.
+        # Cross-thread communication has overhead that varies with system load,
+        # so we use a tolerance of 150ms. This still proves parallelism because
+        # serial execution would show deltas of 200ms+ (the sleep interval).
+        assert math.isclose(delta_time, 0, abs_tol=0.15) is True, (
             f"delta_time: {delta_time}"
         )