CI: Keep centos:7 at actions/checkout@v3

Author: andreasabel

.github/workflows/ci.yml

@@ -54,7 +54,8 @@ jobs:
       run: |
         yum install -y gcc gmp gmp-devel make ncurses ncurses-compat-libs xz perl autoconf
         curl --proto '=https' --tlsv1.2 -sSf https://get-ghcup.haskell.org | BOOTSTRAP_HASKELL_NONINTERACTIVE=1 BOOTSTRAP_HASKELL_GHC_VERSION=9.2.8 sh
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v3
+        # actions/checkout@v4 (using node20) does not run on image: centos:7
     - name: Test
       run: |
         source ~/.ghcup/env