Revert "specify R version"

This reverts commit 6308df5.

Author: lorenzwalthert

.github/workflows/benchmarking.yaml

@@ -35,22 +35,12 @@ jobs:
         run: git branch $GITHUB_BASE_REF remotes/origin/$GITHUB_BASE_REF; git branch
       - name: Setup R
         uses: r-lib/actions/setup-r@master
-        with:
-          r-version: ${{ matrix.config.r }}
       - name: Query dependencies
         run: |
           install.packages('remotes')
           saveRDS(remotes::dev_package_deps(dependencies = TRUE), ".github/depends.Rds", version = 2)
           writeLines(sprintf("R-%i.%i", getRversion()$major, getRversion()$minor), ".github/R-version")
         shell: Rscript {0}
-      - name: Cache R packages
-        if: runner.os != 'Windows'
-        uses: actions/cache@v1
-        with:
-          path: ${{ env.R_LIBS_USER }}
-          key: ${{ runner.os }}-${{ hashFiles('.github/R-version') }}-1-${{ hashFiles('.github/depends.Rds') }}
-          restore-keys: ${{ runner.os }}-${{ hashFiles('.github/R-version') }}-1-
-
       - name: Install system dependencies
         if: runner.os == 'Linux'
         env: