Bump actions/checkout from 2 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/sumaform-validation.yml

@@ -12,7 +12,7 @@ jobs:
     name: Validate sumaform files
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - id: tf_files
         name: Get modified .tf files
@@ -31,7 +31,7 @@ jobs:
         with:
           tofu_version: 1.10.7
       - name: Checkout sumaform
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           repository: maximenoel8/sumaform
           path: sumaform

.github/workflows/test-environment-cleaner-validation.yml

@@ -11,7 +11,7 @@ jobs:
 
     steps:
       - name: Validate api manager script
-        uses: actions/checkout@v2
+        uses: actions/checkout@v6
 
       - name: Set up Python 3.11
         uses: actions/setup-python@v2