Fix log_handler docstring type for consistency

The Copilot reviewer noted that the log_handler parameter docstring
in TaskHubGrpcWorker.__init__ used optional[logging.Handler], which
is not valid typing syntax and was inconsistent with the surrounding
parameters' X | None, optional form (a pre-existing lowercase typo
that the typing-modernization regex didn't catch).

Normalize it to logging.Handler | None, optional to match the style
used for all other parameters in the docstring.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: Bernd Verst

durabletask/worker.py

@@ -442,7 +442,7 @@ class TaskHubGrpcWorker:
             Defaults to the value from environment variables or localhost.
         metadata (list[tuple[str, str]] | None, optional): gRPC metadata to include with
             requests. Used for authentication and routing. Defaults to None.
-        log_handler (optional[logging.Handler]): Custom logging handler for worker logs. Defaults to None.
+        log_handler (logging.Handler | None, optional): Custom logging handler for worker logs. Defaults to None.
         log_formatter (logging.Formatter | None, optional): Custom log formatter.
             Defaults to None.
         secure_channel (bool, optional): Whether to use a secure gRPC channel (TLS).