Remove useless/deprecated CI step

Author: kelson42

.github/workflows/ci.yml

@@ -93,10 +93,6 @@ jobs:
     container:
       image: "ghcr.io/kiwix/kiwix-build_ci_${{matrix.image_variant}}:2023-10-30"
     steps:
-    - name: Extract branch name
-      shell: bash
-      run: echo "##[set-output name=branch;]$(echo ${GITHUB_REF#refs/heads/})"
-      id: extract_branch
     - name: Checkout code
       uses: actions/checkout@v4
     - name: Install dependencies