feat: To update and upgrade pylint checker

[msampathkumar]

Is your feature request related to a problem? Please describe.

Feature request to update https://github.com/GoogleCloudPlatform/python-docs-samples/blob/main/.kokoro/docker/Dockerfile

Describe the solution you'd like.

1. The current testing framework includes checks for Python 3.7 and Python 3.8, which are unmaintained. So there is a immediate need for this docker to be updated. Expected outcome is removing support for these outdated versions.

2. Request to consider alternatives like RUFF to pylint. Given the size of this repository, a linter like RUFF would be cost effective + faster.

Describe alternatives you've considered.

NA

Additional context.

NA

Thanks!