ci: bump actions/upload-artifact from 5 to 6 (#457)

Bumps [actions/upload-artifact](https://github.com/actions/upload-artifact) from 5 to 6.
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](actions/upload-artifact@v5...v6)

---
updated-dependencies:
- dependency-name: actions/upload-artifact
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/interop.yml

@@ -68,7 +68,7 @@ jobs:
         docker save $URL | gzip --best > ${{ matrix.image }}.tar.gz
         du -sh ${{ matrix.image }}.tar.gz
     - name: Upload result
-      uses: actions/upload-artifact@v5
+      uses: actions/upload-artifact@v6
       with:
         name: images-${{ matrix.image }}
         path: ${{ matrix.image }}.tar.gz
@@ -95,7 +95,7 @@ jobs:
           docker save $URL | gzip --best > ${{ matrix.image }}.tar.gz
           du -sh ${{ matrix.image }}.tar.gz
       - name: Upload result
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         with:
           name: image-${{ matrix.image }}
           path: ${{ matrix.image }}.tar.gz
@@ -184,7 +184,7 @@ jobs:
           remote_user: ${{ secrets.INTEROP_SEEMANN_IO_USER }}
           remote_key: ${{ secrets.INTEROP_SEEMANN_IO_SSH_KEY }}
       - name: Upload result
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         with:
           name: results-${{ matrix.server }}-${{ matrix.client }}
           if-no-files-found: error
@@ -218,7 +218,7 @@ jobs:
       - name: Print result
         run: jq '.' result.json
       - name: Upload result to artifacts
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         with:
           name: result-aggregated
           path: result.json