test(streamable-http): move resumption count assertion into coroutine for py311 coverage

Author: mrutunjay-kinagi

tests/shared/test_streamable_http.py

@@ -1846,11 +1846,10 @@ async def exercise_client() -> None:
             terminate_on_close=False,
         ):
             await anyio.sleep(0)
+        unittest.TestCase().assertEqual(start_count, 1, f"Expected exactly one GET stream start, got {start_count}")
 
     anyio.run(exercise_client)
 
-    unittest.TestCase().assertEqual(start_count, 1, f"Expected exactly one GET stream start, got {start_count}")
-
 
 @pytest.mark.anyio
 async def test_priming_event_not_sent_for_old_protocol_version():