Bump node-fetch from 2.6.0 to 2.6.1 in /.azure-pipelines-preproduction (

Azure#10762)

Bumps [node-fetch](https://github.com/bitinn/node-fetch) from 2.6.0 to 2.6.1.
- [Release notes](https://github.com/bitinn/node-fetch/releases)
- [Changelog](https://github.com/node-fetch/node-fetch/blob/master/docs/CHANGELOG.md)
- [Commits](node-fetch/node-fetch@v2.6.0...v2.6.1)

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