docs: Refine and fix nits in README

[kelbrown20]

Description: Refines and fixes some nits in the Llama stack readme

[leseb]

@kelbrown20 can you look at the precommit error? Please run it locally

[kelbrown20]

@leseb Yeah i'm looking into that and a bit unsure whats going on bc its passing locally but not in the PR.

[cdoern]

@kelbrown20 it looks like pre-commit is adding back some of the indentation changes you made, they might be purposeful for formatting?

[kelbrown20]

I think you're right bc it was the pre-commit that added those indentations to the PR, so should this be okay?

[ashwinb]

@kelbrown20 please run pre-commit locally. Without that, it will be much harder to get the whitespacing right. You need python=3.12, pre-commit>=4.4.0