Bump actions/checkout from 2 to 4

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]>

Author: dependabot[bot]

.github/workflows/master.yml

@@ -27,7 +27,7 @@ jobs:
     strategy:
       matrix: ${{ fromJSON(needs.generate-matrix.outputs.matrix) }}
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - uses: haskell-actions/setup@v2
       id: setup-haskell-cabal
       name: Setup Haskell
@@ -96,7 +96,7 @@ jobs:
     runs-on: "ubuntu-latest"
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - uses: cachix/install-nix-action@v20
       with:
         extra_nix_config: |