Bringing minimum python version up to 3.9 to match dbt-core

[hiloboy0119]

Problem

The minimum version of python for this package is set up at 3.8 where dbt-core requires 3.9

Solution

Updated all relevant files to require python 3.9 or higher

Checklist

• [x] I have read the contributing guide and understand what's expected of me
• [x] I have run this code in development and it appears to resolve the stated issue
• [x] This PR includes tests, or tests are not required/relevant for this PR
• [x] This PR has no interface changes (e.g. macros, cli, logs, json artifacts, config files, adapter interface, etc) or this PR has already received feedback and approval from Product or DX

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[cla-bot[bot]]

Thank you for your pull request and welcome to our community. We could not parse the GitHub identity of the following contributors: Drew Goya. This is most likely caused by a git client misconfiguration; please make sure to:

1. check if your git client is configured with an email to sign commits git config --list | grep email
2. If not, set it up using git config --global user.email email@example.com
3. Make sure that the git commit email is configured in your GitHub account settings, see https://github.com/settings/emails