build(deps): bump node-fetch and cross-fetch

Bumps [node-fetch](https://github.com/node-fetch/node-fetch) to 2.7.0 and updates ancestor dependency [cross-fetch](https://github.com/lquixada/cross-fetch). These dependencies need to be updated together.


Updates `node-fetch` from 2.6.1 to 2.7.0
- [Release notes](https://github.com/node-fetch/node-fetch/releases)
- [Commits](node-fetch/node-fetch@v2.6.1...v2.7.0)

Updates `cross-fetch` from 3.0.6 to 3.1.8
- [Release notes](https://github.com/lquixada/cross-fetch/releases)
- [Changelog](https://github.com/lquixada/cross-fetch/blob/v3.1.8/CHANGELOG.md)
- [Commits](lquixada/cross-fetch@v3.0.6...v3.1.8)

---
updated-dependencies:
- dependency-name: node-fetch
  dependency-type: indirect
- dependency-name: cross-fetch
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>