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] <[email protected]>

Author: dependabot[bot]

.github/workflows/ci.yaml

@@ -134,7 +134,7 @@ jobs:
         run: env
 
       - name: Download package
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with:
           name: dist-packages
           path: dist
@@ -298,7 +298,7 @@ jobs:
     runs-on: ubuntu-24.04
     steps:
       - name: Download distribution files
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with:
           name: dist-packages
           path: dist
@@ -344,7 +344,7 @@ jobs:
       id-token: write
     steps:
       - name: Download distribution files
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with:
           name: dist-packages
           path: dist