bug#43122: 27.1; hep text

[Per Starbäck]

In GNU Emacs 27.1:

emacs -Q
(setq help-window-select t) C-j
C-x 2
C-h k M-x

The *Help* buffer appears. In the echo area I get a message

  Type "q" to restore previous buffer, M-x scroll-up to scroll help.

It would be nicer it if told me to use C-v for scrolling, so in
lisp/help.el I think scroll-up-command should be used instead of
scroll-up.