chore(deps): 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/build.yml

@@ -206,7 +206,7 @@ jobs:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
 
       - name: ⏬Download all the build artifacts
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with:
           path: release-artifacts
 

.github/workflows/jextract.yml

@@ -77,7 +77,7 @@ jobs:
         run: rm -rf jextract/src || true
 
       - name: 📥 Download source artifacts
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with:
           path: jextract/src