checkers/spell: fix default ispell dict
checkers/spell: fix default ispell dict

Changes the default ispell dictionary from "en" to "english" since the
former isn't actually a default dictionary name listed in ispell. See
https://github.com/emacs-mirror/emacs/blob/9f30a6b1a417cebe795956a7eef44b8cd9b71557/lisp/textmodes/ispell.el#L471

Otherwise, enabling checkers/spell doesn't do anything even if aspell and the
aspell-en dictionary are installed according to the module README file.

hlissner/doom-emacs,hlissner/doom-emacs,hlissner/doom-emacs,hlissner/.emacs.d,hlissner/.emacs.d,hlissner/.emacs.d,hlissner/doom-emacs,hlissner/.emacs.d,hlissner/.emacs.d,hlissner/.emacs.d,hlissner/doom-emacs,hlissner/.emacs.d,hlissner/doom-emacs,hlissner/.emacs.d,hlissner/doom-emacs