Bump @saucelabs/visual from 0.6.4 to 0.6.6 in /storybook (#695)

Bumps @saucelabs/visual from 0.6.4 to 0.6.6.

---
updated-dependencies:
- dependency-name: "@saucelabs/visual"
  dependency-type: indirect
  update-type: version-update:semver-patch
...

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