CFHT clean up connection pool

`aeonlib.osc.facility.OCSFacility` does this:
`
    def __init__(self, settings: Settings = default_settings):
...
        self.client: httpx.Client = httpx.Client(
            base_url=self.api_root(settings), headers=headers
        )

    def __del__(self):
       self.client.close()`


CFHTFacility needs the `__del__()` so it cleans up the connection pool also.