Uses setup-node@v4 when running the test workflow

Version 4 runs on Node20.

See also:

- https://github.com/actions/setup-node/releases/tag/v4.0.0

.github/workflows/test.yml

@@ -14,7 +14,7 @@ jobs:
       - name: Get the sources
         uses: actions/checkout@v1
       - name: Install Node 20
-        uses: actions/setup-node@v3
+        uses: actions/setup-node@v4
         with:
           node-version: '20'
       - name: Install the .NET 6 SDK