Bump actions/checkout from 2 to 3 (#863)

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 3.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2...v3)

---
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>

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -15,7 +15,7 @@ jobs:
   rubocop:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - uses: ruby/setup-ruby@v1
         with:
           ruby-version: '3.0'
@@ -33,7 +33,7 @@ jobs:
         model-parser: [grape-swagger-entity, grape-swagger-representable, '']
     steps:
     - name: Check out branch
-      uses: actions/checkout@v2
+      uses: actions/checkout@v3
     - name: Set up Ruby
       uses: ruby/setup-ruby@v1
       with: