Improve documentation of Info node movement commands

* lisp/info.el (Info-next, Info-prev, Info-forward-node)
(Info-backward-node): More detailed descriptions of what each
commands does with respect to child and parent nodes.  (Bug#42050)
1 job for emacs-27 in 60 minutes and 11 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #6467
test-all

01:00:11