[py] Fix type hint

Author: cgoldberg

py/selenium/webdriver/common/virtual_authenticator.py

@@ -80,7 +80,7 @@ def __init__(
         self,
         credential_id: bytes,
         is_resident_credential: bool,
-        rp_id: str,
+        rp_id: Optional[str],
         user_handle: Optional[bytes],
         private_key: bytes,
         sign_count: int,