[readme] replace runkit CI badge with shields.io check-runs badge

Author: ljharb

README.md

@@ -71,7 +71,7 @@ Simply clone the repo, `npm install`, and run `npm test`
 [downloads-url]: https://npm-stat.com/charts.html?package=@es-shims/api
 [codecov-image]: https://codecov.io/gh/es-shims/es-shim-api/branch/main/graphs/badge.svg
 [codecov-url]: https://app.codecov.io/gh/es-shims/es-shim-api/
-[actions-image]: https://img.shields.io/endpoint?url=https://github-actions-badge-u3jn4tfpocch.runkit.sh/es-shims/es-shim-api
+[actions-image]: https://img.shields.io/github/check-runs/es-shims/es-shim-api/main
 [actions-url]: https://github.com/es-shims/es-shim-api/actions
 [es-abstract-url]: https://npmjs.com/package/es-abstract
 [define-properties-url]: https://npmjs.com/package/define-properties