Update font scaling documentation to not talk about "face height"

Update font scaling documentation to not talk about "face height"

* lisp/play/gamegrid.el (gamegrid-init-buffer):
* lisp/mwheel.el (mouse-wheel-scroll-amount):
(mouse-wheel-text-scale):
* lisp/faces.el (set-face-attribute):
* lisp/face-remap.el (text-scale-mode-step):
(text-scale-increase):
(text-scale-adjust):
* lisp/cus-face.el (custom-face-attributes):
* doc/emacs/frames.texi (Mouse Commands):
* doc/emacs/display.texi (Text Scale): Talk about font sized instead
of "face height" (bug#46853).