Use Super-Linter Slim Image

[jbampton]

So far we are only using the Flake8 linter so we don't need the full image.

Should improve workflow time.

https://github.com/github/super-linter#slim-image

Description

Types of changes

• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Bug fix (non-breaking change which fixes an issue)
• [X] Enhancement (improves an existing feature and functionality)
• [ ] Cleanup (Code refactoring and cleanup, that may add test cases)

Feature/Enhancement Scale or Bug Severity

Feature/Enhancement Scale

• [ ] Major
• [X] Minor

Bug Severity

• [ ] BLOCKER
• [ ] Critical
• [ ] Major
• [ ] Minor
• [X] Trivial

Screenshots (if appropriate):

How Has This Been Tested?