Prevent error output from passing test

[dandavison]

Prevent error ouptut from test. See #801 (comment)

tests/worker/test_update_with_start.py .

================================================================================================= 1 passed in 0.54s ==================================================================================================
Future exception was never retrieved
future: <Future finished exception=RPCError('empty details')>
Traceback (most recent call last):
  File "/Users/dan/src/temporalio/sdk-python/tests/worker/test_update_with_start.py", line 843, in test_start_update_with_start_empty_details
    await client.start_update_with_start_workflow(
  File "/Users/dan/src/temporalio/sdk-python/temporalio/client.py", line 1048, in start_update_with_start_workflow
    return await self._start_update_with_start(
  File "/Users/dan/src/temporalio/sdk-python/temporalio/client.py", line 1120, in _start_update_with_start
    return await self._impl.start_update_with_start_workflow(input)
  File "/Users/dan/src/temporalio/sdk-python/temporalio/client.py", line 6113, in start_update_with_start_workflow
    raise err
  File "/Users/dan/src/temporalio/sdk-python/temporalio/client.py", line 6059, in start_update_with_start_workflow
    return await self._start_workflow_update_with_start(
  File "/Users/dan/src/temporalio/sdk-python/temporalio/client.py", line 6149, in _start_workflow_update_with_start
    await self._client.workflow_service.execute_multi_operation(multiop_req)
  File "/Users/dan/src/temporalio/sdk-python/tests/worker/test_update_with_start.py", line 836, in __call__
    raise self.empty_details_err
temporalio.service.RPCError: empty details

[THardy98]

nice!