Bump actions/checkout from 3 to 4

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] <support@github.com>

Author: dependabot[bot]

.github/workflows/cabal.yml

@@ -19,7 +19,7 @@ jobs:
         os: [ubuntu-latest]
     name: Cabal with GHC ${{ matrix.ghc }}
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Setup Haskell
         uses: haskell-actions/setup@v2
         with:
@@ -46,7 +46,7 @@ jobs:
   #       os: [ubuntu-latest]
   #   name: Cabal with GHC ${{ matrix.ghc }} and mtl >= 2.3.1
   #   steps:
-  #     - uses: actions/checkout@v3
+  #     - uses: actions/checkout@v4
   #     - name: Setup Haskell
   #       uses: haskell/actions/setup@v2
   #       with:

.github/workflows/haskell-ci.yml

@@ -149,7 +149,7 @@ jobs:
           chmod a+x $HOME/.cabal/bin/cabal-plan
           cabal-plan --version
       - name: checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           path: source
       - name: initial cabal.project for sdist

.github/workflows/nix-flake.yml

@@ -17,7 +17,7 @@ jobs:
     name: Nix on ${{ matrix.os }}
     runs-on: ${{ matrix.os }}
     steps:
-    - uses: actions/checkout@v3.5.3
+    - uses: actions/checkout@v4
     - uses: cachix/install-nix-action@v22
       with:
         extra_nix_config: |