Update `slp` for removed `mon` flags
Update `slp` for removed `mon` flags

I think the rewrite of `bin/mon` removed the `--check` flag completely,
and calling it without options should do the right thing regardless.

benizi/dotfiles,benizi/dotfiles,benizi/dotfiles,benizi/dotfiles,benizi/dotfiles,benizi/dotfiles,benizi/dotfiles,benizi/dotfiles