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/deploy-api-lambda.yml

@@ -37,7 +37,7 @@ jobs:
       - uses: actions/checkout@v5
 
       - name: Download bootstrap binary
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with:
           name: api-lambda-binary # Defined in build-api-lambda.yml
 

.github/workflows/release.yml

@@ -102,7 +102,7 @@ jobs:
     steps:
 
       - name: Download bootstrap binary
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with: 
           name: link-index-updater-lambda-binary # Defined in build-link-index-updater-lambda.yml