chore(deps): update actions/upload-artifact action to v6

Author: renovate[bot]

.github/workflows/test-build.yml

@@ -48,7 +48,7 @@ jobs:
           zip -r _site.zip ./dist
 
       - name: upload _site artifact
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v6
         with:
           name: _site
           path: _site.zip
@@ -60,7 +60,7 @@ jobs:
 
       - name: Upload PR number
         if: ${{ always() }}
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v6
         with:
           name: pr
           path: ./pr-id.txt