Undo monkey-patching by :func:`inject_into_urllib3`.

def extract_from_urllib3():
    """
    Undo monkey-patching by :func:`inject_into_urllib3`.
    """
    util.ssl_.SSLContext = orig_util_SSLContext
    util.HAS_SNI = orig_util_HAS_SNI
    util.ssl_.HAS_SNI = orig_util_HAS_SNI
    util.IS_SECURETRANSPORT = False
    util.ssl_.IS_SECURETRANSPORT = False