Bump GitHub Actions off deprecated Node 20 runtime

GitHub is force-running Node 20 actions on Node 24 and warns on every deploy.

  actions/checkout               v4 -> v7
  actions/setup-node             v4 -> v7
  actions/configure-pages        v5 -> v6
  actions/upload-pages-artifact  v3 -> v5
  actions/deploy-pages           v4 -> v5

All inputs used here (path, node-version, id) are unchanged across these
majors; the bumps are Node 24 runtime updates and ESM migrations. checkout v7's
behavioural change blocks fork-PR checkout for pull_request_target and
workflow_run, neither of which this workflow uses. checkout v5 requires runner
>= v2.327.1, which ubuntu-latest satisfies.

Also moves node-version from 20 (EOL) to 24. That Node runs 'npx pagefind',
which declares no engine constraint and indexes fine on much newer versions.

ruby/setup-ruby stays at v1 -- it is a rolling major tag, currently v1.321.0.

Author: sbryngelson

.github/workflows/deploy.yml

@@ -19,7 +19,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v7
 
       - name: Set up Ruby
         uses: ruby/setup-ruby@v1
@@ -28,12 +28,12 @@ jobs:
           bundler-cache: true
 
       - name: Set up Node
-        uses: actions/setup-node@v4
+        uses: actions/setup-node@v7
         with:
-          node-version: '20'
+          node-version: '24'
 
       - name: Configure Pages
-        uses: actions/configure-pages@v5
+        uses: actions/configure-pages@v6
 
       - name: Build site
         run: bundle exec jekyll build
@@ -44,7 +44,7 @@ jobs:
         run: npx -y pagefind@1.5.0 --site _site
 
       - name: Upload artifact
-        uses: actions/upload-pages-artifact@v3
+        uses: actions/upload-pages-artifact@v5
         with:
           path: _site
 
@@ -57,4 +57,4 @@ jobs:
     steps:
       - name: Deploy to GitHub Pages
         id: deployment
-        uses: actions/deploy-pages@v4
+        uses: actions/deploy-pages@v5