(devel/R-pkgcache) Updated 2.1.1 to 2.2.1

# pkgcache 2.2.1

* pkgcache now does a better job when matching the R version to a
  Bioconductor version.

# pkgcache 2.2.0

* New `pkg.current_platform` option and `PKG_CURRENT_PLATFORM` environment
  variable to override the detected platform.

* In `repo_add()` and `repo_resolve()` the `MRAN@` prefix is now deprecated
  and resolves to PPM, because MRAN will be retired soon. See more at
  <https://posit.co/blog/migrating-from-mran-to-posit-package-manager/>.

* The metadata cache now has `SystemRequirements` information for Bioconductor
  packages.

(mef)