build(deps): 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](actions/download-artifact@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] <[email protected]>

Author: dependabot[bot]

.github/workflows/staging.yml

@@ -26,7 +26,7 @@ jobs:
         run: doctl registry login --expiry-seconds 600
 
       - name: Download Docker image
-        uses: actions/download-artifact@v5
+        uses: actions/download-artifact@v6
         with:
           name: did-resolver-staging
 
@@ -52,7 +52,7 @@ jobs:
           password: ${{ secrets.GITHUB_TOKEN }}
 
       - name: Download Docker image
-        uses: actions/download-artifact@v5
+        uses: actions/download-artifact@v6
         with:
           name: did-resolver-staging
 

.github/workflows/test.yml

@@ -37,7 +37,7 @@ jobs:
       - uses: actions/checkout@v5
 
       - name: Download Docker image
-        uses: actions/download-artifact@v5
+        uses: actions/download-artifact@v6
         with:
           name: did-resolver-staging