Bump actions/checkout from 4 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...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] <[email protected]>

Author: dependabot[bot]

.github/workflows/build-disk.yml

@@ -49,7 +49,7 @@ jobs:
         uses: ublue-os/remove-unwanted-software@v9
 
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Build ISO
         id: build

.github/workflows/build.yml

@@ -54,7 +54,7 @@ jobs:
           echo "IMAGE_NAME=${IMAGE_NAME,,}" >> ${GITHUB_ENV}
 
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Maximize build space
         uses: ublue-os/remove-unwanted-software@v9