Update Python.gitignore to ignore pixi

[DonJayamanne]

Ignore pixi directory https://github.com/prefix-dev/pixi/blob/main/.gitignore

Reasons for making this change:

Ignore .pixi directory from git.

Links to documentation supporting these rule changes:

See here https://github.com/prefix-dev/pixi/blob/main/.gitignore & here http://8.217.189.46:8067/prefix-dev/pixi/issues/2115

[wirecat]

@DonJayamanne Could you provide more information please? What is pixi and why should .pixi be ignored?

[kasi-x]

wirecat Why has my issue been ignored for such a long time? https://github.com/github/gitignore/pull/4471

[wirecat]

@kasi-x It's not intentional and we're doing our best.

[wirecat]

This is a duplicate of https://github.com/github/gitignore/pull/4471, however https://github.com/github/gitignore/pull/4471 has the documentation I need to properly review this change. Closing this PR in favor of https://github.com/github/gitignore/pull/4471.