build(deps): bump actions/upload-artifact from 4 to 6

Bumps [actions/upload-artifact](https://github.com/actions/upload-artifact) from 4 to 6.
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](actions/upload-artifact@v4...v6)

---
updated-dependencies:
- dependency-name: actions/upload-artifact
  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/release.yml

@@ -44,7 +44,7 @@ jobs:
             recipe: 'recipe.yml'
             plugins: 'Vanilla-OS/vib-fsguard:v1.6.1'
 
-      - uses: actions/upload-artifact@v4
+      - uses: actions/upload-artifact@v6
         with:
             name: Containerfile
             path: Containerfile

.github/workflows/vib-build.yml

@@ -53,7 +53,7 @@ jobs:
         recipe: 'recipe.yml'
         plugins: 'Vanilla-OS/vib-fsguard:v1.6.1'
 
-    - uses: actions/upload-artifact@v4
+    - uses: actions/upload-artifact@v6
       with:
         name: Containerfile
         path: Containerfile
@@ -113,7 +113,7 @@ jobs:
         touch "${{ runner.temp }}/digests/${digest#sha256:}"
 
     - name: Upload digest
-      uses: actions/upload-artifact@v4
+      uses: actions/upload-artifact@v6
       if: ${{ github.event_name != 'pull_request' }}
       with:
         name: digests-${{ matrix.arch }}