Refactor: Remove unused quote_mode parameter from unset_key

Remove the quote_mode parameter from the unset_key function in main.py.
This parameter was identified as unused within the function body and has been removed to simplify the signature.

Author: creepereye1204

src/dotenv/main.py

@@ -200,7 +200,6 @@ def set_key(
 def unset_key(
     dotenv_path: StrPath,
     key_to_unset: str,
-    quote_mode: str = "always",
     encoding: Optional[str] = "utf-8",
 ) -> Tuple[Optional[bool], str]:
     """