Button component hasIconOnly assistive text styling not working

[gptt916]

What package(s) are you using?

• carbon-components
• carbon-components-react

Detailed description

Describe in detail the issue you're having.

When using the Button component and importing the style by using

@import 'carbon-components/scss/components/button/_button';

the assistive text's styling does not work, and is in the wrong position.

Is this issue related to a specific component?

Yes, Button

What did you expect to happen? What happened instead? What would you like to
see changed?

The Button scss should include styling for the assistive text

What browser are you working in?

Firefox

What version of the Carbon Design System are you using?

x.27, reproduced on latest

What offering/product do you work on? Any pressing ship or release dates we
should be aware of?

IBM Cloud Docs

Steps to reproduce the issue

1. Create Button (hasIconOnly) component in js.
2. import Button styling
3. Hover on button

https://codesandbox.io/s/vibrant-sun-i3v25?file=/package.json