Bump generic-array in /assets/dockerfiles/base/rust

Bumps [generic-array](https://github.com/fizyk20/generic-array) from 0.12.3 to 0.12.4.
- [Release notes](https://github.com/fizyk20/generic-array/releases)
- [Changelog](https://github.com/fizyk20/generic-array/blob/0.12.4/CHANGELOG.md)
- [Commits](fizyk20/generic-array@0.12.3...0.12.4)

---
updated-dependencies:
- dependency-name: generic-array
  dependency-type: indirect
...

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Author: dependabot[bot]