Bump actions/checkout from 4 to 5

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 5.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...v5)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '5'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -11,7 +11,7 @@ jobs:
   test-nix-rustls:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - uses: cachix/install-nix-action@v31
         with:
           extra_nix_config: |
@@ -23,7 +23,7 @@ jobs:
   test-nix:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - uses: cachix/install-nix-action@v31
         with:
           extra_nix_config: |
@@ -45,7 +45,7 @@ jobs:
           - '9.10'
           - '9.12'
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - uses: cachix/install-nix-action@v31
       - uses: haskell-actions/setup@v2
         id: setup-haskell