actions: use setup-node@v4 as v3 causes warning

the "Yarn Linting" action causes a warning to appear about a deprecated
Node version. switch to actions/setup-node@v4, which is already in use
by the action building the web app for the firmware, to avoid this
warning.

.github/workflows/yarnlint.yml

@@ -9,7 +9,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - name: Setup Node.js and yarn
-        uses: actions/setup-node@v3
+        uses: actions/setup-node@v4
         with:
           node-version: "18"
           cache: "yarn"