Update version of external workflows

[wileyj]

with current version, we're recieving a lot of deprecation warning. i.e..:

Stacks Core Tests / Unit Tests (2)
Your workflow is using a version of actions/cache that is scheduled for deprecation, actions/cache@0c45773b623bea8c8e75f6c82b208c3cf94ea4f9. Please update your workflow to use either v3 or 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

we'll need to updated these actions to use something more recent.