bump minimum R version R CMD check in GHA workflow to v4.1.0

Author: joshwlambert

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

@@ -59,7 +59,7 @@ jobs:
           - {os: ubuntu-latest,   r: 'devel', http-user-agent: 'release'}
           - {os: ubuntu-latest,   r: 'release'}
           - {os: ubuntu-latest,   r: 'oldrel-1'}
-          - {os: ubuntu-latest,   r: '3.6'}
+          - {os: ubuntu-latest,   r: '4.1'}
 
     env:
       GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}