build: bump actions/download-artifact from 5 to 6

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

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

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/ci.yml

@@ -212,15 +212,15 @@ jobs:
       - uses: actions/checkout@v5
         with:
           persist-credentials: false
-      - uses: actions/download-artifact@v5
+      - uses: actions/download-artifact@v6
         with:
           name: linux-coverage
           path: test/linux
-      - uses: actions/download-artifact@v5
+      - uses: actions/download-artifact@v6
         with:
           name: macos-coverage
           path: test/macos
-      - uses: actions/download-artifact@v5
+      - uses: actions/download-artifact@v6
         with:
           name: e2e-coverage
           path: test/e2e
@@ -441,7 +441,7 @@ jobs:
 
       # Get binary from build step
       - name: Download binary
-        uses: actions/download-artifact@v5
+        uses: actions/download-artifact@v6
         with:
           name: binary