Bump actions/download-artifact from 5.0.0 to 6.0.0

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 5.0.0 to 6.0.0.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](actions/download-artifact@v5.0.0...v6.0.0)

---
updated-dependencies:
- dependency-name: actions/download-artifact
  dependency-version: 6.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/ab-testing-deploy.yml

@@ -32,7 +32,7 @@ jobs:
           deno-version: v2.3
 
       - name: Download build artifact
-        uses: actions/download-artifact@v5.0.0
+        uses: actions/download-artifact@v6.0.0
         with:
           name: ab-testing-build
           path: ab-testing/dist

.github/workflows/ab-testing-ui.yml

@@ -57,7 +57,7 @@ jobs:
         uses: ./.github/actions/setup-node-env
 
       - name: Fetch build
-        uses: actions/download-artifact@v5.0.0
+        uses: actions/download-artifact@v6.0.0
         with:
           name: ui-build
           path: output/ab-tests.html