Refine --as-cran configuration based on code review feedback

Co-authored-by: osorensen <21175639+osorensen@users.noreply.github.com>

Author: Copilot

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

@@ -23,8 +23,8 @@ jobs:
           - {os: ubuntu-latest,   r: 'release'}
           - {os: ubuntu-latest,   r: 'oldrel-1'}
           - {os: windows-latest,  r: 'release'}
-          # Debian-like environment with CRAN checks
-          - {os: ubuntu-latest,   r: 'devel', http-user-agent: 'release', check-as-cran: 'true'}
+          # CRAN-like checks on Debian (using ubuntu-latest with --as-cran)
+          - {os: ubuntu-latest,   r: 'devel', http-user-agent: 'release', as-cran: true}
 
     env:
       GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}
@@ -50,4 +50,4 @@ jobs:
         with:
           upload-snapshots: true
           build_args: 'c("--no-manual","--compact-vignettes=gs+qpdf")'
-          args: ${{ matrix.config.check-as-cran == 'true' && 'c("--as-cran")' || 'c("--no-manual")' }}
+          args: ${{ matrix.config.as-cran && 'c("--as-cran")' || 'c()' }}