ci: upgrade sparse to supported build agents

The `sparse` job still uses the `ubuntu-20.04` runner pool, but that
pool is about to go away, so let's stop using it.

There is no `sparse-22.04` artifact provided by the "Build sparse for
Ubuntu" Azure Pipeline, but that is not necessary anyway because Ubuntu
22.04 has the `sparse` package: https://packages.ubuntu.com/jammy/sparse

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

.github/workflows/main.yml

@@ -446,20 +446,11 @@ jobs:
     if: needs.ci-config.outputs.enabled == 'yes'
     env:
       jobname: sparse
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     concurrency:
       group: sparse-${{ github.ref }}
       cancel-in-progress: ${{ needs.ci-config.outputs.skip_concurrent == 'yes' }}
     steps:
-    - name: Download a current `sparse` package
-      # Ubuntu's `sparse` version is too old for us
-      uses: git-for-windows/get-azure-pipelines-artifact@v0
-      with:
-        repository: git/git
-        definitionId: 10
-        artifact: sparse-20.04
-    - name: Install the current `sparse` package
-      run: sudo dpkg -i sparse-20.04/sparse_*.deb
     - uses: actions/checkout@v4
     - name: Install other dependencies
       run: ci/install-dependencies.sh