Backport: ci: fix failing Test (CGroup V1) (LTS) (#723)

It appears that now the default `remote images` is
https://images.lxd.canonical.com.

I don't know why, but we can't remove `images`.
The following command do nothing, so this step fails.

    lxc remote remove images


ref. #675

Signed-off-by: Daijiro Fukuda <fukuda@clear-code.com>
Co-authored-by: Daijiro Fukuda <fukuda@clear-code.com>

.github/workflows/yum.yml

@@ -123,10 +123,6 @@ jobs:
         with:
           name: packages-${{ matrix.rake-job }}
       - uses: canonical/setup-lxd@v0.1.1
-      - name: Update image server
-        run: |
-          lxc remote remove images
-          lxc remote add images https://images.lxd.canonical.com --protocol=simplestreams
       - name: Run Test ${{ matrix.test-file }} on ${{ matrix.test-lxc-image }}
         run: fluent-package/yum/systemd-test/test.sh ${{ matrix.test-lxc-image }} ${{ matrix.test-file }}