Bump axios and botframework-schema in /example

Removes [axios](https://github.com/axios/axios). It's no longer used after updating ancestor dependency [botframework-schema](https://github.com/Microsoft/botbuilder-js). These dependencies need to be updated together.


Removes `axios`

Updates `botframework-schema` from 4.2.0 to 4.19.1
- [Release notes](https://github.com/Microsoft/botbuilder-js/releases)
- [Commits](microsoft/botbuilder-js@4.2...4.19.1)

---
updated-dependencies:
- dependency-name: axios
  dependency-type: indirect
- dependency-name: botframework-schema
  dependency-type: indirect
...

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Author: dependabot[bot]