Update R-cran-* WWW to modern URL

Old R-cran-* ports have https://cran.r-project.org/web/packages/${PORTNAME}

New R-cran-* ports have https://cran.r-project.org/package=${PORTNAME}

Replace all the old WWW URLs with new WWW URLs

Reviewed by: fuz
Differential Revision: https://reviews.freebsd.org/D59714