Bump form-data in /genkit_flutter_agentic_app/genkit_backend

Bumps  and [form-data](https://github.com/form-data/form-data). These dependencies needed to be updated together.

Updates `form-data` from 4.0.2 to 4.0.4
- [Release notes](https://github.com/form-data/form-data/releases)
- [Changelog](https://github.com/form-data/form-data/blob/master/CHANGELOG.md)
- [Commits](form-data/form-data@v4.0.2...v4.0.4)

Updates `form-data` from 2.5.3 to 4.0.4
- [Release notes](https://github.com/form-data/form-data/releases)
- [Changelog](https://github.com/form-data/form-data/blob/master/CHANGELOG.md)
- [Commits](form-data/form-data@v4.0.2...v4.0.4)

---
updated-dependencies:
- dependency-name: form-data
  dependency-version: 4.0.4
  dependency-type: indirect
- dependency-name: form-data
  dependency-version: 4.0.4
  dependency-type: indirect
...

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

Author: dependabot[bot]