Bump actions/download-artifact from 7 to 8 (#6)

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -19,7 +19,7 @@ jobs:
     steps:
       # No need to checkout the project, since all we need is to download the
       # build artifact from the build step.
-      - uses: actions/download-artifact@v7
+      - uses: actions/download-artifact@v8
         with:
           repository: ${{ env.REPOSITORY }}
           github-token: ${{ secrets.LEON_REPOSITORY_DISPATCH }}