Do not set `MANPAGER` to `nvim` as `nvim-man` is used already and in the
case that it does not open `nvim` I want to use `less` as **pager**.
This makes it possible to use `man -- <page>` as 'hack' to view the page
in `less` for example if a real pager is desired because of the loading
time (e.g. `zshall`).