Update python-test.yaml's ubuntu, postgresql versions to enable dependabot to update django

[bobtabor-msft]

Purpose

• Dependabot is dying because python-test.yaml is using an old version of postgresql (that has been retired) which Django utils can't use any more
• GitHub Actions was brownouting to highlight the need to bump the Ubuntu version from 20.04 to 24.04, the latest LTS
• This fixes both issues, and allows Dependabot to do its thing

Does this introduce a breaking change?

[ ] Yes
[x] No

Pull Request Type

What kind of change does this Pull Request introduce?

[x] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Documentation content changes
[ ] Other... Please describe:

How to Test

• Get the code

fork
run GitHub actions
Enjoy happy success 

• Test the code

What to Check

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Other Information