The old statsrv with R 4.0.4 has finally been retired, and I asked around to confirm that people in VISC and HVTN are no longer using R that old. It sounds like everyone is now on rsrv or newer.

How new of an R version should we require? Well, the tidyverse currently supports R as old as R 4.1.0 as part of their policy of supporting an approximately 5-major-version (~5-year) lookback:

https://github.com/tidyverse/dplyr/blob/main/DESCRIPTION

Which seems reasonable to me.

So, this PR:

• drops the statsrv-mimic CI runner for R 4.0.4, but still keeps a runner on R 4.1.0 with statsrv's old pandoc version (2.11.4).
• adds an explicit rsrv-mimic CI runner using R 4.4.2 and pandoc 3.2.
• adds the R >= 4.1.0 dependency to the VISCfunctions DESCRIPTION. We won't be able to install the new version of VISCfunctions on R older than that.
• switches the package to using the base pipe.

Closes #117