Bump actions/download-artifact from 2 to 6

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 2 to 6.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](actions/download-artifact@v2...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] <[email protected]>

Author: dependabot[bot]

.github/workflows/deploy-storybook.yml

@@ -83,7 +83,7 @@ jobs:
           ref: gh-pages
 
       - name: Download storybook files
-        uses: actions/download-artifact@v2
+        uses: actions/download-artifact@v6
         with:
           name: storybook-files
           path: storybook-files

.github/workflows/tests-karma-editor.yml

@@ -130,7 +130,7 @@ jobs:
           ref: gh-pages
 
       - name: Download coverage file
-        uses: actions/download-artifact@v2
+        uses: actions/download-artifact@v6
         with:
           name: cuj-coverage-edit-story