issue: elastic#163462

## Summary

Change of plan. We are going to delete the button.

~Disable the 'Create Rule' button on the Rule Group page and add the
read icon to the topbar when the user is on read mode.~
Delete 'Create Rule' button on the Rule Group page

### How to reproduce it
* ~Create a role with read access to the security solution feature~
* ~Login with a user that has the created role~
* Open the rule group page

### Checklist

Delete any items that are not applicable to this PR.

- [x] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios

(cherry picked from commit 9aafd1f)