Bump actions/checkout from 6 to 7 (#444)

Bumps [actions/checkout](https://github.com/actions/checkout) from 6 to 7.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v6...v7)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '7'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/CI.yml

@@ -19,10 +19,10 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@v7
 
       - name: Checkout Schemas repo
-        uses: actions/checkout@v6
+        uses: actions/checkout@v7
         with:
           repository: IATI/IATI-Codelists
           ref: version-2.03
@@ -56,7 +56,7 @@ jobs:
       matrix:
         version: [ 2.01, 2.02, 2.03 ]
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@v7
 
       - name: 'Trigger update of Validator Codelists repository for version-${{ matrix.version }}'
         run: |