Clean / Update pr.yml

it seems that this is currently building a > 2gb artifact as it just keeps growing - I'd like to let it clean so we can verify if this is the whole issue, we can go back to true after. We'd need to rerun any existing prs

.github/workflows/pr.yml

@@ -32,7 +32,7 @@ jobs:
         with:
           github_token: ${{ secrets.GITHUB_TOKEN }}
           publish_dir: ./_site
-          keep_files: true
+          keep_files: false
       - name: Add deploy link
         uses: actions/github-script@v6
         with: