Build: Bump actions/download-artifact from 7 to 8 (#3109)

Author: dependabot[bot]

.github/workflows/nightly-pypi-build.yml

@@ -74,7 +74,7 @@ jobs:
 
     steps:
     - name: Download all the artifacts
-      uses: actions/download-artifact@v7
+      uses: actions/download-artifact@v8
       with:
         merge-multiple: true
         path: dist/

.github/workflows/python-ci.yml

@@ -197,7 +197,7 @@ jobs:
     - name: Install dependencies
       run: uv sync --group dev
     - name: Download all coverage artifacts
-      uses: actions/download-artifact@v7
+      uses: actions/download-artifact@v8
       with:
         pattern: coverage-*
         merge-multiple: true