docstring for isearch-whitespace-chars

[Per Starback]

GNU Emacs 21.1:

This doesn't matter with standard key bindings, but obviously this is
meant instead:

*** isearch.el.~1.197.~ Thu Oct 18 12:05:34 2001
--- isearch.el  Tue Nov 13 01:26:46 2001
***************
*** 1327,1333 ****
  
  (defun isearch-whitespace-chars ()
    "Match all whitespace chars, if in regexp mode.
! If you want to search for just a space, type \\[quoted-insert] SPC."
    (interactive)
    (if isearch-regexp 
        (if (and search-whitespace-regexp (not isearch-within-brackets)
--- 1327,1333 ----
  
  (defun isearch-whitespace-chars ()
    "Match all whitespace chars, if in regexp mode.
! If you want to search for just a space, type 
\\<isearch-mode-map>\\[isearch-quote-char] SPC."
    (interactive)
    (if isearch-regexp 
        (if (and search-whitespace-regexp (not isearch-within-brackets)