Bump node-fetch and cross-fetch

Bumps [node-fetch](https://github.com/node-fetch/node-fetch) and [cross-fetch](https://github.com/lquixada/cross-fetch). These dependencies needed to be updated together.

Updates `node-fetch` from 2.6.0 to 2.7.0
- [Release notes](https://github.com/node-fetch/node-fetch/releases)
- [Commits](node-fetch/node-fetch@v2.6.0...v2.7.0)

Updates `cross-fetch` from 3.0.4 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@v3.0.4...v3.1.8)

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

Signed-off-by: dependabot[bot] <[email protected]>