feat: To update and upgrade pylint checker

## 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](https://endoflife.date/python). So there is a immediate need for this docker to be updated. Expected outcome is removing support for these outdated versions.

1. Request to consider alternatives like [RUFF](https://github.com/astral-sh/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!