Remove uninformative itertools recipe (pythonGH-100253)

(cherry picked from commit 8356c14)

Co-authored-by: Raymond Hettinger <rhettinger@users.noreply.github.com>

Doc/library/itertools.rst

@@ -790,10 +790,6 @@ which incur interpreter overhead.
        "Count how many times the predicate is true"
        return sum(map(pred, iterable))
 
-   def pad_none(iterable):
-       "Returns the sequence elements and then returns None indefinitely."
-       return chain(iterable, repeat(None))
-
    def ncycles(iterable, n):
        "Returns the sequence elements n times"
        return chain.from_iterable(repeat(tuple(iterable), n))
@@ -1163,9 +1159,6 @@ which incur interpreter overhead.
     >>> take(5, map(int, repeatfunc(random.random)))
     [0, 0, 0, 0, 0]
 
-    >>> list(islice(pad_none('abc'), 0, 6))
-    ['a', 'b', 'c', None, None, None]
-
     >>> list(ncycles('abc', 3))
     ['a', 'b', 'c', 'a', 'b', 'c', 'a', 'b', 'c']