Bump actions/checkout from 5 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 5 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v5...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/build.yml

@@ -37,7 +37,7 @@ jobs:
         run: echo "VERSION=${GITHUB_SHA::7}" >> $GITHUB_ENV
 
       - name: Checkout repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           submodules: true
           token: ${{ secrets.TOOLKIT_SUBMODULES }}

.github/workflows/scripts.yml

@@ -21,7 +21,7 @@ jobs:
     name: Run Parsiphae
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           submodules: true
           token: ${{ secrets.TOOLKIT_SUBMODULES }}

.github/workflows/validation.yml

@@ -22,7 +22,7 @@ jobs:
     name: Run patch validator
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Check for validity
         uses: szapp/patch-validator@v1
         with: