*/R-cran-*: Remove redundant BUILD_DEPENDS on other R-cran ports

[jrm]

Summary

Mk/Uses/cran.mk unconditionally sets NO_BUILD, so nothing runs during
the build phase. The real work, R CMD INSTALL, happens in do-install
when run dependencies have already been installed. Listing R-cran-*
packages in BUILD_DEPENDS, with or without cran:compiles, only installs
these dependencies earlier.

While here:

• math/R-cran-Amelia: move rlang, an Import that was only listed in BUILD_DEPENDS, to RUN_DEPENDS. Bump PORTREVISION.
• math/R-cran-MatchIt: likewise for rlang; drop chk, which 4.8.1 no longer imports; fix the Rcpp entry, which had an empty version (">=") instead of ">=1.0.10". Bump PORTREVISION.
• textproc/R-cran-openxlsx, textproc/R-cran-readxl: drop knitr from BUILD_DEPENDS. It is only a vignette builder and CRAN tarballs ship built vignettes.