deps: 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)
- [Commits](https://github.com/actions/checkout/compare/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>

.github/workflows/build-installer-iso.yml

@@ -16,7 +16,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v6
+        uses: actions/checkout@v6.0.2
 
       - name: Free disk space
         run: |

.github/workflows/build.yml

@@ -42,7 +42,7 @@ jobs:
 
       # These stage versions are pinned by https://github.com/renovatebot/renovate
       - name: Checkout
-        uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v5
 
       # This is optional, but if you see that your builds are way too big for the runners, you can enable this by uncommenting the following lines:
       # - name: Maximize build space