remove remaining imports of typing_extensions

[dotlambda]

Description of change

It's not a dependency anymore: https://github.com/redis/redis-py/blob/fb3095480c794846a906ad2876424e8404ff4b34/pyproject.toml#L31

Pull Request check-list

Please make sure to review and check all of these items:

• [ ] Do tests and lints pass with this change?
• [ ] Do the CI tests pass with this change (enable it first in your forked repo and wait for the github action build to finish)?
• [ ] Is the new or changed code fully tested?
• [ ] Is a documentation update included (if this change modifies existing APIs, or introduces new ones)?
• [ ] Is there an example added to the examples folder (if applicable)?

NOTE: these things are not required to open a PR and can be done afterwards / while the PR is open.

[petyaslavova]

Hi @dotlambda, thank you for your contribution! We will review your change soon.