fix: incorrect mypy diagnosis of Unpack[ExtraArgs].

[JPHutchins]

Fixes #1487 in the simplest way, according to https://peps.python.org/pep-0692/#required-and-non-required-keys. This has the effect of making the BleakScanner ExtraArgs optional instead of required.

For reference:

    class ExtraArgs(TypedDict):
        """
        Keyword args from :class:`~bleak.BleakScanner` that can be passed to
        other convenience methods.
        """

        service_uuids: List[str]
        """
        Optional list of service UUIDs to filter on. Only advertisements
        containing this advertising data will be received. Required on
        macOS >= 12.0, < 12.3 (unless you create an app with ``py2app``).
        """
        scanning_mode: Literal["active", "passive"]
        """
        Set to ``"passive"`` to avoid the ``"active"`` scanning mode.
        Passive scanning is not supported on macOS! Will raise
        :class:`BleakError` if set to ``"passive"`` on macOS.
        """
        bluez: BlueZScannerArgs
        """
        Dictionary of arguments specific to the BlueZ backend.
        """
        cb: CBScannerArgs
        """
        Dictionary of arguments specific to the CoreBluetooth backend.
        """
        backend: Type[BaseBleakScanner]
        """
        Used to override the automatically selected backend (i.e. for a
            custom backend).
        """

[dlech]

Thanks!