Bump actions/upload-artifact from 4 to 6 in /.github/workflows

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] <[email protected]>

Author: dependabot[bot]

.github/workflows/compile-examples.yml

@@ -95,7 +95,7 @@ jobs:
 
       - name: Save memory usage change report as artifact
         if: github.event_name == 'pull_request'
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v6
         with:
           name: sketches-report-${{ matrix.board.artifact-name-suffix }}
           path: ${{ env.SKETCHES_REPORTS_PATH }}

.github/workflows/sync-labels.yml

@@ -70,7 +70,7 @@ jobs:
           file-url: https://raw.githubusercontent.com/arduino/tooling-project-assets/main/workflow-templates/assets/sync-labels/${{ matrix.filename }}
 
       - name: Pass configuration files to next job via workflow artifact
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v6
         with:
           path: |
             *.yaml