Update Doc/library/stdtypes.rst

Co-authored-by: Victor Stinner <vstinner@python.org>

Author: adorilson

Doc/library/stdtypes.rst

@@ -1843,7 +1843,7 @@ expression support in the :mod:`re` module).
    intended to remove all case distinctions in a string. For example, the German
    lowercase letter ``'ß'`` is equivalent to ``"ss"``. Since it is already
    lowercase, :meth:`lower` would do nothing to ``'ß'``; :meth:`casefold`
-   converts it to ``"ss"``. This is useful for case-insensitive string comparisons.
+   converts it to ``"ss"``.
    For example:
 
    .. doctest::