Bump actions/upload-artifact from 5 to 6

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
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

.github/workflows/release.yml

@@ -81,7 +81,7 @@ jobs:
       if: matrix.config.os == 'macos-latest'
 
     - name: upload artifacts
-      uses: actions/upload-artifact@v5
+      uses: actions/upload-artifact@v6
       with:
         name: clang_${{ matrix.config.name }}_${{ matrix.config.arch }}
         path: |
@@ -147,7 +147,7 @@ jobs:
         ninja clang-format clangd
 
     - name: upload artifacts
-      uses: actions/upload-artifact@v5
+      uses: actions/upload-artifact@v6
       with:
         name: clang_${{ matrix.config.name }}_${{ matrix.config.arch }}
         path: |

.github/workflows/sync-labels.yml

@@ -71,7 +71,7 @@ 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@v5
+        uses: actions/upload-artifact@v6
         with:
           path: |
             *.yaml