Fix the dependency on serde

[nox]

The dependencies on serde and serde_macros need a version number.

warning: dependency (serde_macros) specified without providing a local path, Git repository, or version to use. This will be considered an error in future versions
warning: dependency (serde) specified without providing a local path, Git repository, or version to use. This will be considered an error in future versions

[nox]

This actually blocks publishing new releases.