Fix python version 3.7 with architecture x64 not found for Ubuntu 24.04

[slothkong]

Hello @rfdearborn,
First of all, thanks for the awesome work you and your collaborators have done with this GitHub Action.

This PR addresses #26.
The issue is straight forward: Python 3.7 is not any more part of the GitHub runner image tagged as ubuntu-latest (see the image manifest). In fact, is not part of any of the available Ubuntu-base runner images anymore.

I bumped the Python version to 3.12, alongside versions of pre-required GitHub actions. I chose 3.12 as is the latest version for dbt supports (see compatibility matrix). This should cover dbt v1.7+ and dbt v1,8+, including the latest data unittest features.

I have verified that

1. Changes I made do not break the project's tests (see workflow run details)
2. The GitHub action runs end-to-end, using my own dbt project with a CI pipeline using slothkong/dbt-docs-to-notion@main, and my own Notion instance (see [1] and [2])

Let me know if there is anything else I can do to make it easier for the fix to get merged~

[1] Logs of dbt project's CI pipeline

[2] Output in Notion

[rfdearborn]

Lgtm. Thanks!