chore: bump pydantic to v2.5.3

[gruyaume]

Description

Bump pydantic to v2.5.3.

Note

Unfortunately we can't go higher at the moment because the rustc package from the apt repo for Ubuntu 22.04 used in the Charm isn't compatible. You can read more about this here: pydantic/pydantic-core#1176

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have added tests that validate the behaviour of the software
• I validated that new and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have bumped the version of the library