build(deps): bump form-data and appium in /appium (#2766)

Bumps [form-data](https://github.com/form-data/form-data) to 4.0.6 and updates ancestor dependency [appium](https://github.com/appium/appium/tree/HEAD/packages/appium). These dependencies need to be updated together.


Updates `form-data` from 4.0.5 to 4.0.6
- [Release notes](https://github.com/form-data/form-data/releases)
- [Changelog](https://github.com/form-data/form-data/blob/master/CHANGELOG.md)
- [Commits](form-data/form-data@v4.0.5...v4.0.6)

Updates `appium` from 3.5.0 to 3.5.1
- [Release notes](https://github.com/appium/appium/releases)
- [Changelog](https://github.com/appium/appium/blob/master/packages/appium/CHANGELOG.md)
- [Commits](https://github.com/appium/appium/commits/appium@3.5.1/packages/appium)

---
updated-dependencies:
- dependency-name: form-data
  dependency-version: 4.0.6
  dependency-type: indirect
- dependency-name: appium
  dependency-version: 3.5.1
  dependency-type: direct:development
...

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Author: dependabot[bot]