Remove python 3.9 checks from CI tests

[KelvinLinBU]

Closes #217. Removed because of successful tool migration to python 3.12.

[QuanMPhm]

Aside from minor comments below, your commit message needs to be amended. We're removing testing for 3.9 not (directly) because we want to use the latest version of nerc_rates, but because all our other tools (i.e coldfront-plugin-api) has finished migrating to 3.12. Therefore, it is now 'safe' for us to remove testing for 3.9, since we know all our tools should now all work on 3.12

[KelvinLinBU]

@QuanMPhm changes are done

[QuanMPhm]

Your commit message summary is very long. This can cause reading issues on certain GUIs or terminals. As a general rule, try to keep the line length of your commit messages before 80 characters. You can check the commit messages in this repo as an example.

Aside from that, this looks good. @knikolla Just like a quick pass from you. Should the CI files have py312 in their names?

[KelvinLinBU]

Your commit message summary is very long. This can cause reading issues on certain GUIs or terminals. As a general rule, try to keep the line length of your commit messages before 80 characters. You can check the commit messages in this repo as an example.

Aside from that, this looks good. @knikolla Just like a quick pass from you. Should the CI files have py312 in their names?

done