Update link checker action

.github/workflows/linkchecker.yml

@@ -12,11 +12,12 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v2
-    - name: Set up Ruby 2.6
-      uses: actions/setup-ruby@v1
+    - uses: actions/checkout@v4
+    - name: Set up Ruby
+      uses: ruby/setup-ruby@v1
       with:
-        ruby-version: 2.6.x
+        ruby-version: '3.3' # Not needed with a `.ruby-version` or `.tool-versions`
+        bundler-cache: true # runs 'bundle install' and caches installed gems automatically
     - name: Check links
       #FIXME Need to allow duplicates (same links on the same page)
       run: |