CI/AppImage: Drop gcc13 workaround

Been fixed upstream for some time now.

.github/workflows/rolling-release.yml

@@ -198,14 +198,6 @@ jobs:
     runs-on: ubuntu-22.04
     timeout-minutes: 120
     steps:
-    # Work around https://github.com/actions/runner-images/issues/8659
-    - name: Remove GCC 13 from runner image
-      shell: bash
-      run: |
-        sudo rm -f /etc/apt/sources.list.d/ubuntu-toolchain-r-ubuntu-test-jammy.list
-        sudo apt-get update
-        sudo apt-get install -y --allow-downgrades 'libc6=2.35-0ubuntu*' 'libc6-dev=2.35-0ubuntu*' libstdc++6=12.3.0-1ubuntu1~22.04 libgcc-s1=12.3.0-1ubuntu1~22.04
-
     - uses: actions/checkout@v4.1.6
       with:
         fetch-depth: 0