Update actions/upload-artifact action to v4

.github/workflows/renovate.yml

@@ -33,7 +33,7 @@ jobs:
 
       - name: Save log file
         # FIXME: v4 of this action causes an error on Forgejo (“You must configure a GitHub token”)
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         if: always()
         with:
           name: renovate-log.ndjson

.github/workflows/test.yml

@@ -41,7 +41,7 @@ jobs:
           RENOVATE_REPOSITORY_CACHE: 'enabled'
           RENOVATE_TOKEN: ${{ vars.renovate_token }} #${{ github.token }}
 
-      - uses: actions/upload-artifact@v3
+      - uses: actions/upload-artifact@v4
         with:
           name: Renovate log
           path: renovate-log.ndjson