Lower the minimum version for typing-extensions by 1 version (4.8.0 -> 4.7.1)

[sdaves]

This allows stateless to be imported in the browser:

https://jupyterlite.readthedocs.io/en/stable/_static/lab/index.html

# within pyodide (browser WASM python)

import micropip
await micropip.install('stateless')
import stateless
print(dir(stateless))