Refactor existing test

Author: dandavison

tests/worker/test_workflow.py

@@ -4367,7 +4367,7 @@ async def test_workflow_update_before_worker_start(
     )
 
     # Confirm update not there
-    assert not await workflow_update_exists(client, handle.id, "my-update")
+    assert not await update_admitted(client, handle.id, "my-update")
 
     # Execute update in background
     update_task = asyncio.create_task(
@@ -4378,7 +4378,7 @@ async def test_workflow_update_before_worker_start(
 
     # Wait until update exists
     await assert_eq_eventually(
-        True, lambda: workflow_update_exists(client, handle.id, "my-update")
+        True, lambda: update_admitted(client, handle.id, "my-update")
     )
 
     # Start no-cache worker on the task queue