Accordion item heading height, icon spacing, and font style don't match designs

[lazd]

Description

Accordion's heading doesn't match the designs.

Steps to reproduce

1. Go to http://spectrum-css-archives.s3-website.us-east-2.amazonaws.com/2.16.0/docs/accordion.html
2. Screenshot it
3. Compare to XD file here https://www.dropbox.com/sh/6t8so9becymkf55/AACsFVyajcgnOPhAst-bm5hfa?dl=0
4. Note the various mismatches: height, font style, icon spacing

Expected behavior

Font style and spacing between Chevron match

Screenshots

Environment

• Spectrum CSS version: 2.16.0
• Browser(s) and OS(s): Chrome on macOS

Additional context

Discovered while testing #511