Rename at aliases to pt

[ricardoV94]

Description

We used to do import aesara.tensor as at, and for ease we just changed it to pytensor.tensor as at. Since we don't depend directly on any Aesara or Aesara-related library we should go with the new default pytensor.tensor as pt.

[Raj-Parekh24]

Hey @ricardoV94,

I am currently getting acquainted with the repository, I have raised PR for fixes in documentation issue #6569. For this I have set-up the local environment.

Can I take this issue to get myself acquainted with the code base.

[shreyas3156]

Hi, @Raj-Parekh24 I actually just made the changes for this issue and am in the process of submitting a PR.

[Raj-Parekh24]

Ok @shreyas3156,

Thanks for the update.

[shreyas3156]

Hi @ricardoV94, I have created a PR implementing the changes that would close this issue. It would be great if you could review it and provide a feedback as this is my first contribution to this repo.