vim: remove explicit 'keywordprg=:help'
vim: remove explicit 'keywordprg=:help'

This setting is now in vim's own runtime files as off about a year ago
(vim 8.0.1290).

https://github.com/vim/vim/commit/7f2e9d7c9cdfc5201a899b7b610edf64bf80c45f

jparise/dotfiles,jparise/dotfiles,jparise/dotfiles,jparise/dotfiles