CI: use Node.js 21.x (#3399)

21.3 had a bug, but 21.4 should be good.

Author: nstepien

.github/workflows/ci.yml

@@ -16,7 +16,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-node@v4
         with:
-          node-version: '21.2.x'
+          node-version: '21.x'
           check-latest: true
       - uses: actions/cache@v3
         with: