Disable npm cache in docs workflow Node.js setup step.

Author: timhauke

.github/workflows/docs.yml

@@ -26,7 +26,6 @@ jobs:
         uses: actions/setup-node@v6
         with:
           node-version: "18"
-          cache: "npm"
 
       - name: Install Mermaid CLI
         run: npm install -g @mermaid-js/mermaid-cli@10.9.0