build(deps): bump actions/checkout from 3 to 4 (#277)

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/nix.yml

@@ -14,7 +14,7 @@ jobs:
         os: [ ubuntu-20.04, macos-latest ]
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: cachix/install-nix-action@v23
       - uses: cachix/cachix-action@v12
         with:
@@ -31,7 +31,7 @@ jobs:
         os: [ ubuntu-20.04 ] # macos-latest is not working right now
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           # Nix Flakes doesn't work on shallow clones
           fetch-depth: 0
@@ -50,7 +50,7 @@ jobs:
         os: [ ubuntu-20.04 ]
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: cachix/install-nix-action@v23
       - uses: cachix/cachix-action@v12
         with: