Docs: Admonitions not rendering correctly

[NielsPraet]

Currently, admonitions in the numpy docstrings are not rendered correctly on:

mkdocs = "^1.4.3"
mkdocstrings = { version = "^0.20.0", extras = ["python"] }
mkdocs-material = "^9.1.18"

On the mkdocstrings documentation, it is stated that admonitions in docstrings are currently (only) supported in Google docstrings. As this project uses Numpy docstrings, we should follow this up when new mkdocstrings versions release.