bug#54288: 28.0.91; which-func documentation error

[sebastian]

In which-func.el there is the following function:

(defun which-func-update ()
  "Update the Which-Function mode display for all windows."
  ;; (walk-windows 'which-func-update-1 nil 'visible))
  (let ((non-essential t))
    (which-func-update-1 (selected-window))))

The doc string is incorrect, since the function only updates the selected 
window. In fact the doc string is commented out on the 27.2 branch, along with 
the walk-windows implementation. It's unclear to me from the git history why 
this implementation for all windows was commented out in the first place, but 
at the very least the doc string should be updated to correctly reflect the 
current implementation.

Thanks.

Sebastian