Multi select (and likely tag) shouldn't change icon size in focused state

[asudoh]

What package(s) are you using?

• carbon-components
• carbon-components-react

Detailed description

Describe in detail the issue you're having.

@laurenmrice told us in #4119 that:

When clicking on the close icon, the close icon gets smaller. It should always be the same size

Is this issue related to a specific component?

Yes, tag and multi select.

What browser are you working in?

Chrome 77

What version of the Carbon Design System are you using?

v10.7.0

Steps to reproduce the issue

Can be seen at: http://react.carbondesignsystem.com/?path=/story/multiselect--default