ci: merge-multiple option for download-artifact

So that wheels are all downloaded to the current working directory

Author: nfrasser

.github/workflows/python-package.yml

@@ -144,6 +144,8 @@ jobs:
     needs: [build]
     steps:
       - uses: actions/download-artifact@v4
+        with:
+          merge-multiple: true
       - uses: actions/setup-python@v5
         with:
           python-version: "3.10"