Remove Sketch references from Platform and VADS

[babsdenney]

Bug Report

• [x] I’ve searched for any related issues and avoided creating a duplicate issue.

What happened

We got feedback from the #platform-design-system slack channel that there are still references to Sketch in Design System guidance. See the slack channel comment.

What I expected to happen

There should be no references to Sketch in the documentation and should be referencing Figma now.

Reproducing

1. Search on VADS for Sketch
2. Search the Platform Confluence for Sketch

Urgency

How urgent is this request? Please select the appropriate option below and/or provide details

• [ ] This bug is blocking work currently in progress
• [ ] This bug is affecting work currently in progress but we have a workaround
• [ ] This bug is blocking work planned within the next few sprints
• [x] This bug is not blocking any work
• [ ] Other

Details

Remove all references to Sketch that can found on confluence, the Platform, and the VADS.

[caw310]

Hey team! Please add your planning poker estimate with Zenhub @babsdenney @danbrady @LWWright7