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

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

@@ -16,7 +16,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Prepare output directory
         run: mkdir -p output

.github/workflows/build.yml

@@ -44,7 +44,7 @@ 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

.github/workflows/renovate.yml

@@ -20,7 +20,7 @@ jobs:
       pull-requests: write
     steps:
       - name: Checkout
-        uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v5
 
       - name: Self-hosted Renovate
         uses: renovatebot/github-action@b9486682a19fe4ea2dd1263c11b4e0c1fe1838fe # v40.3.2

.github/workflows/validate-brewfiles.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v5
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v5
 
       - name: Set up Homebrew
         uses: Homebrew/actions/setup-homebrew@1ccc07ccd54b6048295516a3eb89b192c35057dc # master

.github/workflows/validate-renovate.yml

@@ -17,7 +17,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v5
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v5
 
       - name: Setup Node.js
         uses: actions/setup-node@53b83947a5a98c8d113130e565377fae1a50d02f # v6