github actions: dont clone/install collabsibleTree

 - From KyleM: You don't need the custom step as long as it can be retrieved from the date-pinned RSPM URL

 - Note: we could add scales 1.3.0 at some point instead (to run more tests in CI), but we have functions available now to skip these. mpn-latest will execute them too so its not much of a risk

.github/workflows/main.yaml

@@ -71,23 +71,13 @@ jobs:
           git clone --branch "$version" --depth 1 \
             https://github.com/metrumresearchgroup/nmrec.git "$tdir"
           echo "NMREC_PKG=local::$tdir" >>$GITHUB_ENV
-      - name: Check out collapsibleTree
-        if: matrix.config.label == 'oldest'
-        shell: bash
-        run: |
-          version=0.1.8
-          tdir=$(mktemp -d)
-          git clone --branch "$version" --depth 1 \
-            https://github.com/cran/collapsibleTree.git "$tdir"
-          echo "COLLAPSIBLETREE_PKG=local::$tdir" >>$GITHUB_ENV
       - uses: r-lib/actions/setup-r-dependencies@v2
         with:
           extra-packages: |
             any::pkgdown
             any::rcmdcheck
             ${{ env.MRGMISC_PKG }}
             ${{ env.NMREC_PKG }}
-            ${{ env.COLLAPSIBLETREE_PKG }}
           upgrade: ${{ matrix.config.label == 'oldest' && 'FALSE' || 'TRUE' }}
       - uses: r-lib/actions/check-r-package@v2
       - name: Check pkgdown