Bump actions/download-artifact from 7 to 8

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 7 to 8.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](actions/download-artifact@v7...v8)

---
updated-dependencies:
- dependency-name: actions/download-artifact
  dependency-version: '8'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/wheels.yaml

@@ -60,7 +60,7 @@ jobs:
           # See https://github.com/pypa/twine/issues/1216
           pip install "twine>=6.1.0" "packaging>=24.2"
       - name: Download sdist
-        uses: actions/download-artifact@v7
+        uses: actions/download-artifact@v8
         with:
           name: artifact-source
           path: dist
@@ -82,7 +82,7 @@ jobs:
       url: https://pypi.org/p/prometheus-xmpp-alerts
     steps:
       - name: Download distributions
-        uses: actions/download-artifact@v7
+        uses: actions/download-artifact@v8
         with:
           merge-multiple: true
           pattern: artifact-*