Update github actions step versions

[spenczar]

The test action workflow is currently failing because of this:

This request has been automatically failed because it uses a deprecated version of actions/cache: v2.1.6. Please update your workflow to use v3/v4 of actions/cache to avoid interruptions. Learn more: https://github.blog/changelog/2024-12-05-notice-of-upcoming-releases-and-breaking-changes-for-github-actions/#actions-cache-v1-v2-and-actions-toolkit-cache-package-closing-down

For example, here: https://github.com/fischor/protogen-python/actions/runs/15662486874

This commit updates all pinned versions to their current latest release, which fixes that particular error.

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This change is part of a trio. In combination with #18 and #20, github actions should go green again; this is working on my fork's 'actions' branch which merges the three: https://github.com/spenczar/protogen-python/actions/runs/15672639439/