ci: update to node 20 for build-ext ci

Author: ikreymer

.github/workflows/buildext.yaml

@@ -16,7 +16,7 @@ jobs:
       - name: Install Node.js, NPM and Yarn
         uses: actions/setup-node@v3
         with:
-          node-version: "18.x"
+          node-version: "20.x"
           cache: "yarn"
 
       - name: Yarn Install