dot/lesskey: Use `-r' instead of `-R'.

dot/lesskey: Use `-r' instead of `-R'.

This seems to handle some kinds of colourized output better.  In
particular, GNU `diff' gets mangled by `less -R': only the first line in
a coloured group ends up actually being coloured.  On the other hand,
`less -r' copes with this properly, maybe because it's actually looking
at the control codes rather than feeding them through without thinking
and then accidentally clobbering their effects.

I don't know why my `less' settings have used `-R', but they have for as
long as I've maintained my profile in Git.  Oh, well.