Replace flyspell-use-mouse-3-for-menu with context-menu-mode (bug#50067)

Replace flyspell-use-mouse-3-for-menu with context-menu-mode (bug#50067)

* doc/emacs/fixit.texi (Spelling): Replace mentions of
flyspell-use-mouse-3-for-menu with context-menu-mode.

* lisp/mouse.el (context-menu-map): Use the function from the
text property context-menu-function at mouse click event.

* lisp/textmodes/flyspell.el (flyspell--set-use-mouse-3-for-menu):
Remove function.
(flyspell-use-mouse-3-for-menu): Remove defcustom added recently in 28.1.
(flyspell-context-menu): New function.
(flyspell-mode): Don't call flyspell--set-use-mouse-3-for-menu.
(flyspell-mode-on): Replace flyspell-use-mouse-3-for-menu
with context-menu-mode.
(make-flyspell-overlay): When context-menu-mode is non-nil,
put overlay context-menu-function with flyspell-context-menu
instead of using keymap flyspell-mouse-map.