gh-69619: also inline the str.isspace note in str.strip

Author: kyo5uke

Doc/library/stdtypes.rst

@@ -2751,11 +2751,9 @@ expression support in the :mod:`re` module).
 
    Return a copy of the string with the leading and trailing characters removed.
    The *chars* argument is a string specifying the set of characters to be removed.
-   If omitted or ``None``, the *chars* argument defaults to removing whitespace.
-   The *chars* argument is not a prefix or suffix; rather, all combinations of its
-   values are stripped.
-
-   Whitespace characters are defined by :meth:`str.isspace`.
+   If omitted or ``None``, the *chars* argument defaults to removing whitespace,
+   that is characters for which :meth:`str.isspace` is true.  The *chars* argument
+   is not a prefix or suffix; rather, all combinations of its values are stripped.
 
    For example: