Changed arg type for compatibility with Client class

[RenanGreca]

Description

When using the Worker class from this library, the Python type checker would complain about a mismatch between the temporallib.Client and temporalio.Client types in the arguments. I changed the argument to accept either type, as they are equivalent for that purpose.

I also fixed a mistake in the classdoc, which described Worker as a wrapper to Client.

Engineering checklist

• Documentation updated
• Have tested the workflow works as expected

[kelkawi-a]

I don't believe Python 3.8 doesn't support |, you'd need to use from typing import Union and do Union[Client, TemporalClient]. Could you please test the lib locally with a sample workflow run to ensure it works as intended?

General note: we could do with an integration test for this lib.