Drop GCC 4.8 CI

The workaround to use an old Node version no longer works: actions/checkout#1590

.github/workflows/ci.yml

@@ -160,38 +160,6 @@ jobs:
           git submodule update --init --checkout --depth 1
           time make test262
 
-  linux-gcc48:
-    runs-on: ubuntu-latest
-    container:
-      image: ubuntu:18.04
-    # Work around an issue where the node from actions/checkout is too new
-    # to run inside the old container image.
-    env:
-      ACTIONS_ALLOW_USE_UNSECURE_NODE_VERSION: true
-    steps:
-      - name: install dependencies
-        run: |
-          apt update && apt -y install make gcc-4.8 cmake software-properties-common
-          # git in default ppa repository is too old to run submodule checkout
-          add-apt-repository -y ppa:git-core/ppa
-          apt update && apt install -y git
-      - name: checkout
-        uses: actions/checkout@v3
-        with:
-          submodules: true
-      - name: build
-        env:
-          CC: gcc-4.8
-        run: |
-          mkdir build
-          cd build
-          cmake ..
-          cd ..
-          make -C build -j$(getconf _NPROCESSORS_ONLN)
-      - name: stats
-        run: |
-          ./build/qjs -qd
-
   windows-msvc:
     runs-on: windows-latest
     strategy: