feat: use node-v18 for insider workflow [skip ci]

.github/workflows/insider-spearhead.yml

@@ -25,7 +25,7 @@ jobs:
       - name: Setup Node.js environment
         uses: actions/setup-node@v3
         with:
-          node-version: '16'
+          node-version: '18'
 
       - name: Clone VSCode repo
         run: . get_repo.sh