Warnings regarding truth value of Quantities

When importing/running GLEAM this issue arises:
```
WARNING: AstropyDeprecationWarning: The truth value of a Quantity is ambiguous. In the future this will raise a ValueError. [astropy.units.quantity]
```
This was noticed by @Victor-Savu  in #9. 
Preliminary investigations indicate the issue is caused by how Pydantic dataclasses interact with Astropy Quantities.