build(deps): bump actions/upload-pages-artifact from 1 to 2

Bumps [actions/upload-pages-artifact](https://github.com/actions/upload-pages-artifact) from 1 to 2.
- [Release notes](https://github.com/actions/upload-pages-artifact/releases)
- [Commits](actions/upload-pages-artifact@v1...v2)

---
updated-dependencies:
- dependency-name: actions/upload-pages-artifact
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/github-page.yml

@@ -80,7 +80,7 @@ jobs:
         done
 
     - name: Upload artifacts
-      uses: actions/upload-pages-artifact@v1
+      uses: actions/upload-pages-artifact@v2
       with:
         path: ./haddocks