Button component doesn't match pajamas spec

There might already be an issue to address this but, the button component in storybook doesn't appear to match the specs in Pajamas.

In gitlab!32193 (comment 346008138), we noticed the following:

• The button component height is less than the dropdown component height so that, when both are on the page, they are noticeably different sizes. From the pajamas specs, it looks like they should both be 32px tall?
• The primary success button has bold text, but the design doesn't.

I'm assuming we could just fix the height and the text decoration on the button and that it would fix this issue? Here's what we're seeing when we use the button component:

We also noticed an unexpected shadow on the button that appears on hover: