Only run Python3.6 contrib tests

[owais]

Description

We do not need to run the entire contrib test matrix on core. We need enough confidence that core API changes don’t break anything in contrib. It should be enough to run each test suite on just one version of Python to achieve that. So for core, we can run only Python3.6 contrib workflows. That should be more than enough IMO to ensure nothing breaks in core.

Also disabled contrib docker tests as contrib unit tests should be enough to catch any breakage.

Type of change

Please delete options that are not relevant.

• Dev/Tooling enhancement
• 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 not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• Existing Tests

Does This PR Require a Contrib Repo Change?

Answer the following question based on these examples of changes that would require a Contrib Repo Change:

• Yes. - Link to PR:
• No.

Checklist:

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added
• Documentation has been updated