Fix checkdoc warnings in which-key.el

Fix checkdoc warnings in which-key.el

* lisp/which-key.el (which-key, which-key-idle-secondary-delay)
(which-key-replacement-alist)
(which-key-allow-multiple-replacements, which-key-show-docstrings)
(which-key-highlighted-command-list, which-key-show-prefix)
(which-key-sort-order, which-key-sort-uppercase-first)
(which-key-use-C-h-commands, which-key-show-early-on-C-h)
(which-key-preserve-window-configuration, which-key-C-h-map)
(which-key-delay-functions, which-key-inhibit-regexps)
(which-key-faces, which-key-key-face, which-key-separator-face)
(which-key-note-face, which-key-command-description-face)
(which-key-local-map-description-face, which-key-special-key-face)
(which-key-inhibit-display-hook)
(which-key-this-command-keys-function, which-key-mode)
(which-key--init-buffer, which-key--get-menu-item-binding)
(which-key--get-keymap-bindings, which-key-reload-key-sequence)
(which-key-show-major-mode, which-key-show-full-major-mode)
(which-key-C-h-dispatch): Fix checkdoc warnings.