Bump actions/download-artifact from 3 to 4

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 3 to 4.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](actions/download-artifact@v3...v4)

---
updated-dependencies:
- dependency-name: actions/download-artifact
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/docs.yml

@@ -138,7 +138,7 @@ jobs:
 
       # Fetch the built docs from the "build" job
       - name: Download HTML documentation artifact
-        uses: actions/download-artifact@v3
+        uses: actions/download-artifact@v4
         with:
           name: docs-${{ github.sha }}
           path: doc/_build/html

.github/workflows/pypi.yml

@@ -95,7 +95,7 @@ jobs:
 
       # Fetch the built archives from the "build" job
       - name: Download built archives artifact
-        uses: actions/download-artifact@v3
+        uses: actions/download-artifact@v4
         with:
           name: pypi-${{ github.sha }}
           path: dist