GHA: allow r-pkgs to be built from source

Author: t-kalinowski

.github/workflows/R-CMD-check.yaml

@@ -54,7 +54,7 @@ jobs:
     continue-on-error: ${{ matrix.tf == 'nightly' || contains(matrix.tf, 'rc') || matrix.r == 'devel' }}
     env:
       R_REMOTES_NO_ERRORS_FROM_WARNINGS: 'true'
-      R_COMPILE_AND_INSTALL_PACKAGES: 'never'
+      # R_COMPILE_AND_INSTALL_PACKAGES: 'never' # commented out until CRAN builds TF 2.8
       GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}
 
     steps: