Remove dead code

Author: thisisnic

dev/tasks/r/github.linux.arrow.version.back.compat.yml

@@ -100,17 +100,9 @@ jobs:
 
       - name: Prepare RSPM
         run: |
-          old_arrow_version_major=$(echo ${OLD_ARROW_VERSION} | cut -d. -f1)
-          if [ ${old_arrow_version_major} -ge 6 ]; then
-            # Binary arrow packages for Ubuntu 22.04 are available only
-            # for 6.0.0 or later.
-            rspm="https://packagemanager.rstudio.com/cran/__linux__/jammy/latest"
-            echo "RSPM=${rspm}" >> $GITHUB_ENV
-          else
             # testthat requires fs which now requires libuv1-dev. Install it
             # when RSPM isn't available
             sudo apt update && sudo apt install -y -V libuv1-dev
-          fi
       - uses: r-lib/actions/setup-r@v2
         with:
           r-version: {{ '${{ matrix.config.r }}' }}