build(deps): bump bn.js and @safe-global/api-kit in /frontend

Removes [bn.js](https://github.com/indutny/bn.js). It's no longer used after updating ancestor dependency [@safe-global/api-kit](https://github.com/safe-global/safe-core-sdk). These dependencies need to be updated together.


Removes `bn.js`

Updates `@safe-global/api-kit` from 1.3.1 to 4.0.1
- [Release notes](https://github.com/safe-global/safe-core-sdk/releases)
- [Commits](https://github.com/safe-global/safe-core-sdk/commits)

---
updated-dependencies:
- dependency-name: bn.js
  dependency-version: 
  dependency-type: indirect
- dependency-name: "@safe-global/api-kit"
  dependency-version: 4.0.1
  dependency-type: direct:production
...

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Author: dependabot[bot]