ci: remove any mention of ROOT for consumer tests

It seems some jobs include ROOT in DYLD_LIBRARY_PATH, while others
don't, even if those jobs are part of the same matrix. Not sure
what this correlates to, but jobs which have ROOT in DYLD_LIBRARY_PATH
tend to succeed, whereas those that don't tend to fail. In any case,
we shouldn't need ROOT for consumer build tests, which lately have
been failing the most often.

.github/workflows/ci.yml

@@ -497,7 +497,6 @@ jobs:
     needs:
       - download_test_data
       - build_hipo
-      - build_root
       - build_iguana
     runs-on: ${{ inputs.runner }}
     container:
@@ -520,11 +519,6 @@ jobs:
         with:
           key: ${{ needs.build_hipo.outputs.key }}
           path: hipo.tar.zst
-      - name: get local dependency `ROOT`
-        uses: actions/cache/restore@v4
-        with:
-          key: ${{ needs.build_root.outputs.key }}
-          path: root.tar.zst
       - name: get iguana build artifacts
         uses: actions/download-artifact@v4
         with:
@@ -542,8 +536,6 @@ jobs:
       - name: set cmake prefix path
         if: ${{ matrix.tool == 'cmake' }}
         run: echo CMAKE_PREFIX_PATH=$(pwd)/hipo >> $GITHUB_ENV
-      - name: source environment for ROOT
-        run: .github/source-ROOT.sh root ${{ inputs.runner }} ld # needed for `ld` path
       - name: source iguana environment
         run: source iguana/bin/this_iguana.sh --verbose --githubCI
       ### build test