Add missing types to FSHook

[lmarvaud]

Fix mypy error :

error: Call to untyped function "FSHook" in typed context  [no-untyped-call]

When using :

fs_hook = FSHook(fs_conn_id)

---

^ Add meaningful description above

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[boring-cyborg]

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[pankajastro]

Can you please also fix for sensor init method ?https://github.com/apache/airflow/blob/main/airflow/sensors/filesystem.py#L48

[boring-cyborg]

Awesome work, congrats on your first merged pull request!