[aur-general] nanoc3 deletion request

[Jeremy Audet]

> Just remember there is actually no use for replaces in the aur.  That
directive is only useful in the regular repositories.   Provides and
conflicts is all you actually need for a clean update.
>
> Replaces is used by pacman to find if there is anything in the
repositories that replaces something else.  Like when we did all the
renames of python packages.

Thanks for the tip. I had no idea that `replaces` was only useful in the
reular repositories. I'll add a `conflicts` directive to the ruby-nanoc
package.