Remove filterwarning settings for pytest

Motivation

We used to mark all warnings as errors for our pytest runner with the intention that it'll surface deprecation warnings (so that we can fix them as soon as possible). However, with the changes in the project, it becomes difficult for us to keep up with addressing the deprecation warnings, and our CI often fails because of this.

Changes proposed

Remove the setting to turn warnings as errors so that we can leave them there until people have time to address them.

Test Plan

Please provide clear instructions on how the changes were verified. Attach screenshots if applicable.

Types of changes

[ ] Docs change / refactoring / dependency upgrade
[x] Bug fix (non-breaking change which fixes an issue)
[ ] New feature (non-breaking change which adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist

[x] My code follows the code style of this project.
[x] My change requires a change to the documentation.
[x] I have updated the documentation accordingly.
[x] I have read the CONTRIBUTING document.
[x] I have added tests to cover my changes.
[x] All new and existing tests passed.
[x] The title of my pull request is a short description of the requested changes.

facebookresearch / beanmachine