Add R/4.4.1-gfbf-2023b to selection list

R/4.4.1-gfbf-2023b was compiled with an updated toolchain version which makes installation of some packages smoother. The gfbf toolchain does not include the ScaLAPACK or OpenMPI modules compared to the foss toolchain used to compile most of the other R packages, but I'm not sure how relevant that is for R itself. If it becomes an issue for some users, we can either advise them to load the relevant OpenMPI and ScaLAPACK modules manually or recompile the module with the foss-2023b toolchain. Either way works