ci: update image path

Author: h2xd

.github/workflows/_tests.yml

@@ -45,6 +45,6 @@ jobs:
         uses: actions/upload-artifact@v3
         with:
           name: visual-test-screenshots
-          path: artifacts/image_diffs
+          path: ./testing/artifacts/image_diffs
           if-no-files-found: ignore
           retention-days: 2