Bump node-fetch from 2.6.1 to 2.6.7 in /src/SignalR/clients/ts/FunctionalTests (#42427)

* Bump node-fetch in /src/SignalR/clients/ts/FunctionalTests

Bumps [node-fetch](https://github.com/node-fetch/node-fetch) from 2.6.1 to 2.6.7.
- [Release notes](https://github.com/node-fetch/node-fetch/releases)
- [Commits](https://github.com/node-fetch/node-fetch/compare/v2.6.1...v2.6.7

)

---
updated-dependencies:
- dependency-name: node-fetch
  dependency-type: indirect
...

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* Undo changes for local `npm` dependencies
- apply suggestions from code review

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Co-authored-by: Doug Bunting <6431421+dougbu@users.noreply.github.com>