CI: Update actions/checkout to v4

This means that the workflow will now use Node.JS 20 (instead of Node.JS 16)

See https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/

.github/workflows/build-each-commit.yml

@@ -5,7 +5,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout the repository
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
       - name: Enable Corepack
         run: corepack enable
       - name: Install dependencies using yarn