Update to ubuntu-20.04

[mattleibow]

Description of Change

Just updating things because warnings are not cool!

Bugs Fixed

• warnings

API Changes

None.

Behavioral Changes

None.

Required skia PR

None.

PR Checklist

• [ ] Has tests (if omitted, state reason in description)
• [ ] Rebased on top of main at time of PR
• [ ] Merged related skia PRs
• [ ] Changes adhere to coding standard
• [ ] Updated documentation