use macos-latest runner (and Posit Package Manager repo) for R v4.1 testing (#261)

Author: cjyetman

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

@@ -23,7 +23,7 @@ jobs:
       matrix:
         config:
           - {os: macos-latest,   r: 'release'}
-          - {os: macos-13,   r: '4.1'}
+          - {os: macos-latest,   r: '4.1'}
 
           - {os: windows-latest, r: 'release'}
           - {os: windows-latest, r: '4.1'}
@@ -52,6 +52,7 @@ jobs:
           r-version: ${{ matrix.config.r }}
           http-user-agent: ${{ matrix.config.http-user-agent }}
           use-public-rspm: true
+          extra-repositories: 'https://packagemanager.posit.co/cran/latest'
 
       - uses: r-lib/actions/setup-r-dependencies@v2
         with: