GHA: stop manually configuring RSPM

Author: t-kalinowski

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

@@ -57,12 +57,6 @@ jobs:
       GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}
 
     steps:
-      - name: Configure RSPM
-        if: runner.os == 'Linux'
-        shell: bash
-        run: |
-          RSPM="https://packagemanager.rstudio.com/all/__linux__/$(lsb_release -cs)/latest"
-          echo "RSPM=$RSPM" >> $GITHUB_ENV
 
       - uses: actions/checkout@v2
 
@@ -71,7 +65,7 @@ jobs:
         with:
           r-version: ${{ matrix.r }}
           Ncpus: '2L'
-          crayon.enabled: 'TRUE'
+          use-public-rspm: true
 
       - uses: r-lib/actions/setup-pandoc@v2