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](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/infrastructure-download-external.yml

@@ -77,7 +77,7 @@ jobs:
       matrix:  ${{steps.json.outputs.JSON_CONTENT}}
     steps:
       - name: "Checkout Armbian build Framework"
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           repository: armbian/build
           ref: ${{ inputs.REFERENCE || inputs.branch || 'main' }}
@@ -115,7 +115,7 @@ jobs:
     steps:
 
       - name: Checkout build repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           repository: armbian/build
           fetch-depth: 1
@@ -205,7 +205,7 @@ jobs:
             "rm -rf storage/artifacts/*"
 
       - name: Checkout Armbian OS repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           repository: armbian/os
           path: os
@@ -392,7 +392,7 @@ jobs:
           gpg_private_key: ${{ secrets.GPG_KEY2 }}
 
       - name: Checkout Armbian OS scripts
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           repository: armbian/os
           path: os
@@ -401,7 +401,7 @@ jobs:
           clean: false
 
       - name: Checkout Armbian build script
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           repository: armbian/build
           path: build