Description of the problem

Stickler CI checks the code style for each PR, and leaves comments if there are any styling issues. The configuration file is .stickler.yml. It's configured to run "flake8" to check code styles.

When we submit a PR, we usually don't care about the code style until it's ready to merge. That's why I find the comments annoying. As we already have a CI checking code styles, all PRs won't be merged if they don't follow the code styles.

I think it's safe to remove the Stickler CI service and rely on the github action style checking job instead.