remove no longer referenced footnote

Author: gpshead

Doc/library/datetime.rst

@@ -2795,5 +2795,3 @@ Notes:
 .. [#] See R. H. van Gent's `guide to the mathematics of the ISO 8601 calendar
        <https://web.archive.org/web/20220531051136/https://webspace.science.uu.nl/~gent0113/calendar/isocalendar.htm>`_
        for a good explanation.
-
-.. [#] Passing ``datetime.strptime('Feb 29', '%b %d')`` will fail since 1900 is not a leap year.