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

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.