Fix return type hint for `Query.get()`

Fix return type hint for `Query.get()`

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`Query[_T].get(...)` should return `Optional[_T]` instead of `Optional[Any]`. This is typed correctly when migrating to  `Session.get(_T, ...)`. By typing the legacy `Query.get(...)` call first, it should make migrations easier on developers, as it splits up the type checking improvements (and subsequent errors which may be discovered) from the `Query.get()`
 to `Session.get()` migration.

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This pull request is:

- [x] A documentation / typographical / small typing error fix
	- Good to go, no issue or tests are needed
- [ ] A short code fix
	- please include the issue number, and create an issue if none exists, which
	  must include a complete example of the issue.  one line code fixes without an
	  issue and demonstration will not be accepted.
	- Please include: `Fixes: #<issue number>` in the commit message
	- please include tests.   one line code fixes without tests will not be accepted.
- [ ] A new feature implementation
	- please include the issue number, and create an issue if none exists, which must
	  include a complete example of how the feature would look.
	- Please include: `Fixes: #<issue number>` in the commit message
	- please include tests.

**Have a nice day!**

Closes: #13028
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/13028
Pull-request-sha: 38ec0c3ae072f8c7b62134dd017579a6a249219f

Change-Id: I7ae8e59bc0bd0a25c65de3804d60f6c2b6f50151
(cherry picked from commit 9cd9b6b5896333f779f484c73f3c1119448305b5)