Remove configuration from Redux store

[themeblvd]

Now that we're server-side rendering all of the configuration data into index.html of the admin client app, we no longer need to make an API request to get that data. And with the utility functions added at /utils/data.js it no longer needs to be a part of the state of the Redux store.

So the entire reducer in /admin/src/store/config.js can be removed.