Bump cross-spawn and serverless in /backend

Removes [cross-spawn](https://github.com/moxystudio/node-cross-spawn). It's no longer used after updating ancestor dependency [serverless](https://github.com/serverless/serverless). These dependencies need to be updated together.


Removes `cross-spawn`

Updates `serverless` from 3.38.0 to 4.4.10
- [Release notes](https://github.com/serverless/serverless/releases)
- [Changelog](https://github.com/serverless/serverless/blob/main/CHANGELOG.md)
- [Commits](serverless/serverless@v3.38.0...v4.4.10)

---
updated-dependencies:
- dependency-name: cross-spawn
  dependency-type: indirect
- dependency-name: serverless
  dependency-type: direct:production
...

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Author: dependabot[bot]