Clear our destination directories before copying files to GitHub pages. (#10869)

This should fix stale deleted files being still accessible.

.github/workflows/docs.yaml

@@ -61,6 +61,5 @@ jobs:
         uses: peaceiris/actions-gh-pages@068dc23d9710f1ba62e86896f84735d869951305 # v3.8.0
         with:
           github_token: ${{ secrets.GITHUB_TOKEN }}
-          keep_files: true
           publish_dir: ./book
           destination_dir: ./${{ steps.vars.outputs.branch-version }}

changelog.d/10869.doc

+Properly remove deleted files from GitHub pages when generating the documentation.