gh-38111: GH Actions: Fix upload of macOS wheels to PyPI

    
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The change made in #37099 to accommodate the new design of
actions/{up,down}load-artifact@v4 broke the upload of macOS wheels to
PyPI (see https://github.com/sagemath/sage/actions/runs/9234698750/job/2
5408786962#step:8:23); this was masked so far because the build of macOS
wheels was broken until #36525.

Here we revert to using a separate job that uploads all platform wheels.
This uses the new keywords `pattern` and `merge-multiple` of
actions/download-artifact@v4

Example run:
https://github.com/mkoeppe/sage/actions/runs/9291646178/job/25572343853

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URL: #38111
Reported by: Matthias Köppe
Reviewer(s): Kwankyu Lee

.github/workflows/dist.yml

@@ -240,6 +240,20 @@ jobs:
           name: ${{ matrix.os }}-${{ matrix.arch }}-wheels
           path: ./wheelhouse/*.whl
 
+  upload_wheels:
+    # This needs to be a separate job because pypa/gh-action-pypi-publish cannot run on macOS
+    needs: build_wheels
+    runs-on: ubuntu-latest
+    env:
+      CAN_DEPLOY: ${{ secrets.SAGEMATH_PYPI_API_TOKEN != '' }}
+    steps:
+
+      - uses: actions/download-artifact@v4
+        with:
+          pattern: "*-*-wheels"
+          path: wheelhouse
+          merge-multiple: true
+
       - uses: pypa/gh-action-pypi-publish@release/v1
         with:
           user: __token__