Bump actions/checkout from 3 to 4 (geminabox#559)

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

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

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

.github/workflows/gem-push.yml

@@ -13,7 +13,7 @@ jobs:
       packages: write
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: Set up Ruby 3.1
       uses: ruby/[email protected]
       with:

.github/workflows/prettier.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-22.04
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: Prettier JS
       run: |
         npm install [email protected]

.github/workflows/ruby.yml

@@ -39,7 +39,7 @@ jobs:
             continue-on-error: true
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: Set up Ruby
       uses: ruby/[email protected]
       with:
@@ -73,7 +73,7 @@ jobs:
   rubocop:
     runs-on: ubuntu-20.04
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: Set up Ruby
       uses: ruby/[email protected]
       with: