chore(deps): 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]>

.github/workflows/documentation.yml

@@ -6,7 +6,7 @@ jobs:
   docs:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
       with:
         ref: ${{ github.event.pull_request.head.ref }}
 

.github/workflows/push-terraform-module-version.yaml

@@ -7,7 +7,7 @@ jobs:
   push-terraform-module-version:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: ministryofjustice/cloud-platform-environments/cmd/push-terraform-module-version@main
         env:
           API_URL: ${{ vars.TERRAFORM_MODULE_VERSIONS_API_URL }}

.github/workflows/unit.yml

@@ -11,7 +11,7 @@ jobs:
         runs-on: ubuntu-latest
         steps:
             - name: Checkout
-              uses: actions/checkout@v2
+              uses: actions/checkout@v4
             - name: Setup Terraform
               uses: hashicorp/setup-terraform@v1
               with: