lpulley has created PR #2591: Loosen `AsyncClientSession.with_transaction` callback type in mongo-python-driver

Issue Text:

1. 1. Summary

`AsyncClientSession.with_transaction`'s `callback` is typed as `Callable[[AsyncClientSession], Coroutine[Any, Any, _T]]` but does not use any of `Coroutine`'s interface that isn't already provided in its parent, `Awaitable`.

In other words: at runtime, any function that returns an `Awaitable` works as `callback`, but `callback`'s type unnecessarily requires that the function's return type matches `Coroutine`.

The type should be changed from `Callable[[AsyncClientSession], Coroutine[Any, Any, _T]]` to `Callable[[AsyncClientSession], Awaitable[_T]]` so that a non-`Coroutine` `Awaitable` can be used as `callback`.

1. 1. Changes in this PR

Changed the type of `AsyncClientSession.with_transaction`'s `callback` argument from `Callable[[AsyncClientSession], Coroutine[Any, Any, _T]]` to `Callable[[AsyncClientSession], Awaitable[_T]]`.

1. 1. Testing Plan

Type-checking should cover this change.

1. 1. Checklist
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      1. Checklist for Author

• [ ] Did you update the changelog (if necessary)?
• [ ] Is the intention of the code captured in relevant tests?
• [ ] If there are new TODOs, has a related JIRA ticket been created?

1. 1. 1. Checklist for Reviewer {@primary_reviewer}

• [ ] Does the title of the PR reference a JIRA Ticket?
• [ ] Do you fully understand the implementation? (Would you be comfortable explaining how this code works to someone else?)
• [ ] Have you checked for spelling & grammar errors?
• [ ] Is all relevant documentation (README or docstring) updated?