[Global reset] Fix reset of button styles

[cchaos]

I noticed that the font-size of the links in our Props docs table were way too big and found that I was originally too heavy-handed with the new global styles for Emotion. Previously, it just set everything to inherit, while in the new file I applied our actual font styles. This broke the EuiLink font-size inheritance if the link was actually a <button> and rendered inside of a sized EuiText block.

Before

After

This PR pulls that button selector out of the input-specific font global styles and just applies the necessary font-family. It also ensure font-size inheritance by adding it to the reset file.

Checklist

• Check against all themes for compatibility in both light and dark modes
• Checked in mobile
• Checked in Chrome, Safari, Edge, and Firefox
• [ ] Props have proper autodocs and playground toggles
• [ ] Added documentation
• [ ] Checked Code Sandbox works for any docs examples
• [ ] Added or updated jest and cypress tests
• [ ] Checked for breaking changes and labeled appropriately
• [ ] Checked for accessibility including keyboard-only and screenreader modes
• A changelog entry exists and is marked appropriately

[kibanamachine]

Preview documentation changes for this PR: https://eui.elastic.co/pr_5452/

[thompsongl]

Used the preview link to confirm the fix; LGTM