build(deps-dev): refactor unnecessary usage of typing-extensions and remove it from the dev-dependencies

[ruancomelli]

Since this project requires Python>=3.8, we can always import Protocol directly from typing, making typing-extensions unnecessary.

This PR replaces typing-extensions with typing in the only place it was used and removes typing-extensions from the list of direct dev dependencies of the project.

[msiemens]

Thank you 🙂