Upgrade: Bump actions/deploy-pages from 1 to 2 (mysticatea#35)

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

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

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/GHPages.yml

@@ -48,4 +48,4 @@ jobs:
 
       - name: Deploy to GitHub Pages
         id: deployment
-        uses: actions/deploy-pages@v1
+        uses: actions/deploy-pages@v2