Bump actions/download-artifact from 4 to 6

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 4 to 6.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](actions/download-artifact@v4...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>

Author: dependabot[bot]

.github/workflows/ship.yaml

@@ -261,7 +261,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Download all binaries
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with:
           pattern: cli-binary-*
           path: cli
@@ -273,7 +273,7 @@ jobs:
           tar -tvf cli.tar.gz
 
       - name: Download manifest entries
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with:
           path: entries
 
@@ -307,7 +307,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
-      - uses: actions/download-artifact@v4
+      - uses: actions/download-artifact@v6
         with:
           name: release-artifacts
           path: release/artifacts