math/R: Update to version 4.0.0
Upstream changes:
https://stat.ethz.ch/pipermail/r-announce/2020/000653.html
Also bump PORTREVISION of ports that depend on math/R.
Submitted by: wen (in part)
Reviewed by: jwb, Rainer Hurling <rhurlin@gwdg.de>, thierry
Differential Revision: https://reviews.freebsd.org/D24572