Hide `kappa_ia_nla`

[paddyroddy]

Describe the Bug

Clearly between #21 being raised and merged, https://github.com/glass-dev/cosmology changed its functionality. For now, we will hide this from the users.

To Reproduce

import glass
...

Expected Behaviour

No response

Actual Behaviour

No response

Version In Use

2024.2.dev122+g663f80a.d20241108

Additional Context

- Python version:
- Operating system:

[Saransh-cpp]

We should create an issue to un-hide this function once things start working (just to ensure that we don't forget its existence).

[paddyroddy]

Good idea