fix icon size issue with inherited box sizing

[deloreyj]

Closes #1042

✅ Pull Request Checklist:

• Included link to corresponding React Spectrum GitHub Issue.
• Added/updated unit tests and storybook for this change (for new code or code which already has tests).
• Filled out test instructions.
• Updated documentation (if it already exists for this component).
• Looked at the Accessibility Practices for this feature - Aria Practices

📝 Test Instructions:

Render an Action Button with an icon on a page with this style rule applied. Verify the icon is sized correctly

* {
  box-sizing: inherit;
}

Since this is an edge case style-only code change, what type of test would y'all like?

🧢 Your Project:

Adobe - Magento