build(deps): bump actions/checkout from 2 to 4 (pubgrub-rs#200)

Bumps [actions/checkout](https://github.com/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)

---
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/cargo_publish_dry_run.yml

@@ -13,7 +13,7 @@ jobs:
     name: Publishing works
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - name: Install stable Rust
         uses: actions-rs/toolchain@v1
         with:

.github/workflows/ci.yml

@@ -58,7 +58,7 @@ jobs:
     runs-on: ubuntu-latest
     if: github.event_name != 'pull_request' || github.event.action == 'enqueued'
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
         with:
           fetch-depth: 0
       - name: Check commit conventions

.github/workflows/deploy_documentation.yml

@@ -12,7 +12,7 @@ jobs:
   deploy_documentation:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - name: Install nightly
         uses: actions-rs/toolchain@v1
         with: