"Expand" buttons on Kubernetes page don't work

Summary

In GitLab 12.1 "Expand" buttons on Kubernetes page don't work

Steps to reproduce

Open an exiting Kubernetes cluster's page, locate "Kubernetes cluster details" or "Advanced settings" section and click Expand. Nothing happens.

What is the current bug behavior?

The button does not work

What is the expected correct behavior?

The buttons shall expand corresponding sections