[INTERNAL] Docs: Prevent updating 404.html

An updated version of the 404.html will be deployed from the `main` branch
via #1250.

Author: matz3

.github/workflows/deploy-docs.yml

@@ -20,10 +20,10 @@ jobs:
 
     steps:
     - name: Checkout
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
 
     - name: Use Node.js LTS 20.x
-      uses: actions/setup-node@v5.0.0
+      uses: actions/setup-node@v6
       with:
         node-version: 20.x
 
@@ -50,7 +50,7 @@ jobs:
         npm run schema-workspace-generate
 
     - name: Checkout gh-pages
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
       with:
         ref: gh-pages
         path: gh-pages
@@ -60,7 +60,6 @@ jobs:
         cp -R ./site/schema ./gh-pages/
         rm -rf ./gh-pages/$MIKE_VERSION/api
         cp -R ./site/api ./gh-pages/$MIKE_VERSION/
-        cp ./scripts/resources/custom404.html ./gh-pages/404.html
     - name: Publish Docs
       run: |
         cd ./gh-pages