Simplify usability-testing-how-to to for designers

[rrhyne]

fix direct links

[sourcegraph-bot]

Notifying subscribers in CODENOTIFY files for diff 09ed4ea...22522d0.

Notify	File(s)
@sqs	content/departments/product/design/research/usability-testing-how-to.md

[github-actions]

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[github-actions]

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