Bump actions/checkout from 1 to 4 (#75)

Bumps [actions/checkout](https://github.com/actions/checkout) from 1 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v1...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/ci.yml

@@ -33,7 +33,7 @@ jobs:
           - x64
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
       - name: R Setup
         uses: r-lib/actions/setup-r@v2
         with:

.github/workflows/yasg.yml

@@ -26,7 +26,7 @@ jobs:
       - uses: julia-actions/setup-julia@latest
         with:
           version: ${{ matrix.julia-version }}
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v4
       - name: Instantiate `format` environment and format
         run: |
           julia --project=format -e 'using Pkg; Pkg.instantiate()'