chore(deps-dev): bump @types/react-loadable in /superset-frontend

Bumps [@types/react-loadable](https://github.com/DefinitelyTyped/DefinitelyTyped/tree/HEAD/types/react-loadable) from 5.5.4 to 5.5.6.
- [Release notes](https://github.com/DefinitelyTyped/DefinitelyTyped/releases)
- [Commits](https://github.com/DefinitelyTyped/DefinitelyTyped/commits/HEAD/types/react-loadable)

---
updated-dependencies:
- dependency-name: "@types/react-loadable"
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

superset-frontend/package.json

@@ -231,7 +231,7 @@
     "@types/react-gravatar": "^2.6.8",
     "@types/react-json-tree": "^0.6.11",
     "@types/react-jsonschema-form": "^1.7.4",
-    "@types/react-loadable": "^5.5.4",
+    "@types/react-loadable": "^5.5.6",
     "@types/react-redux": "^7.1.10",
     "@types/react-router-dom": "^5.1.5",
     "@types/react-select": "^3.0.19",