Use persist-credentials: false in example

Since this snippet is meant to be exemplary, it makes sense to
explicitly set `persist-credentials` to `false`. The default value is
`true`.

Author: landongrindheim

_posts/2023-12-14-trusted-publishing.md

@@ -37,6 +37,8 @@ jobs:
     steps:
       # Set up
       - uses: actions/checkout@v4
+        with:
+          persist-credentials: false
       - name: Set up Ruby
         uses: ruby/setup-ruby@v1
         with: