[aur-general] Rename aur/lejos to aur/lejos-rcx

[Zack Buhman]

Hello, I am the current maintainer of both aur/lejos and aur/lejos-rcx.

As promised, I updated the ancient aur/lejos PKGBUILD to something
that is actually working on a modern arch system, as well as the
latest/last upstream release.

Simultaneously, I would like to rename the package to its "lejos-rcx"
retronym to reduced ambiguity between it and its lejos-nxj
counterpart.

Thank you.