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/setup.yaml

@@ -10,7 +10,7 @@ jobs:
     name: Initialise OpenSAFELY project.
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - name: Update README.md and remove action
         shell: bash
         run: |

.github/workflows/test_runner.yaml

@@ -12,6 +12,6 @@ jobs:
     name: Test the project can run, using dummy data
     steps:
     - name: Checkout
-      uses: actions/checkout@v4
+      uses: actions/checkout@v5
     - name: Test that the project is runnable
       uses: opensafely-core/research-action@v2