Bump the updates group with 3 updates (#722)

Bumps the updates group with 3 updates: [actions/checkout](https://github.com/actions/checkout), [actions/cache](https://github.com/actions/cache) and [peaceiris/actions-gh-pages](https://github.com/peaceiris/actions-gh-pages).


Updates `actions/checkout` from 2 to 4
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2...v4)

Updates `actions/cache` from 3 to 4
- [Release notes](https://github.com/actions/cache/releases)
- [Changelog](https://github.com/actions/cache/blob/main/RELEASES.md)
- [Commits](actions/cache@v3...v4)

Updates `peaceiris/actions-gh-pages` from 3 to 4
- [Release notes](https://github.com/peaceiris/actions-gh-pages/releases)
- [Changelog](https://github.com/peaceiris/actions-gh-pages/blob/main/CHANGELOG.md)
- [Commits](peaceiris/actions-gh-pages@v3...v4)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '4'
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: updates
- dependency-name: actions/cache
  dependency-version: '4'
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: updates
- dependency-name: peaceiris/actions-gh-pages
  dependency-version: '4'
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: updates
...

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

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -7,8 +7,8 @@ jobs:
     runs-on: ubuntu-latest
     container: ruby:3-buster
     steps:
-      - uses: actions/checkout@v2
-      - uses: actions/cache@v3
+      - uses: actions/checkout@v4
+      - uses: actions/cache@v4
         with:
           path: vendor/bundle
           key: ${{ runner.os }}-gems-${{ hashFiles('**/Gemfile.lock') }}

.github/workflows/github-pages.yml

@@ -15,8 +15,8 @@ jobs:
     runs-on: ubuntu-latest
     container: ruby:2-buster
     steps:
-      - uses: actions/checkout@v2
-      - uses: actions/cache@v3
+      - uses: actions/checkout@v4
+      - uses: actions/cache@v4
         with:
           path: vendor/bundle
           key: ${{ runner.os }}-gems-${{ hashFiles('**/Gemfile.lock') }}
@@ -30,7 +30,7 @@ jobs:
         run: bundle exec jekyll build
 
       - name: Deploy static site to gh-pages branch.
-        uses: peaceiris/actions-gh-pages@v3
+        uses: peaceiris/actions-gh-pages@v4
         with:
           github_token: ${{ secrets.GITHUB_TOKEN }}
           publish_dir: ./_site