Python: drop a Returns section from a method that returns None - #10168

Motivation & Context

Executor.execute is annotated -> None and returns nothing, but its docstring still advertises a return value:

        Returns:
            An awaitable that resolves to the result of the execution.

The wording survived from an earlier shape of this method: the coroutine now resolves to None after the handlers have been dispatched. Because execute is the method every workflow internals path goes through, the stale sentence is the first thing a reader sees when they open the base class to find out how a message reaches a handler.

Description & Review Guide

• What are the major changes? Removes the Returns: section of WorkflowExecutor.execute (python/packages/core/agent_framework/_workflows/_executor.py). Nothing else changes: no signature, no default, no behaviour, no tests.
• What is the impact of these changes? Documentation only. python-api-compatibility and the typing jobs are unaffected because no annotation moves.
• What do you want reviewers to focus on? Whether removing the section is preferable to rewording it. I removed it because the method genuinely produces no value; if you would rather keep a sentence for symmetry with the Args: block, a one-line "Returns nothing; send results through runner_context." is an equally small diff.

Evidence that the documented value does not exist:

• async def execute(self, message, source_executor_ids, state, runner_context, ...) -> None — the annotation is None.
• The only internal call site, _edge_runner.py:147, does await target_executor.execute(...) and discards the result.
• A repository-wide search for = await …\.execute( finds middleware pipelines, the AG-UI intent owner, and database cursors — no caller of this method reads a value.

Related Issue

N/A - trivial change. One docstring section removed on a method that returns None; no design decision is involved and the diff is three deleted lines.

AI Assistance

• This is an AI-assisted contribution. I reviewed, understood, and verified all submitted content and accept responsibility for it.

AI assistance details: the stale section was located with a static check that reports Returns: blocks in functions whose body never returns a value, and documentation assistance (this description) was used. The finding itself was confirmed by hand against the signature and the single internal call site listed above.

Contribution Checklist

• The code builds clean without any errors or warnings
• All unit tests pass, and I have added new tests where possible
• The PR follows the Contribution Guidelines
• This PR links to an agreed issue with no competing open PR, or the Related Issue section documents a trivial-change exception.
• This is not a breaking change.