Go back to not cleaning when we deploy pkgdown

Author: jennybc

.github/workflows/pkgdown.yaml

@@ -53,6 +53,6 @@ jobs:
         if: github.event_name != 'pull_request'
         uses: JamesIves/github-pages-deploy-action@v4.5.0
         with:
-          clean: true
+          clean: false
           branch: gh-pages
           folder: docs