Update actions/cache to v4.2.2

[mkannwischer]

Github recently turned off their old caching APIs: 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.
liboqs' CI started failing with the following error message for me: This request has been automatically failed because it uses a deprecated version of actions/cache: e12d46a63a90f2fae62d114769bbf2a179198b5c. Please update your workflow to use v3/v4 of actions/cache to avoid interruptions.

This commit updates to the newer version of actions/cache that is using the new Github APIs.

Note that Github's blog post is misleading. A lot more versions than v1/v2 are being disabled including v3.3.3 that is used in liboqs - see actions/cache#1510

• Does this PR change the input/output behaviour of a cryptographic algorithm (i.e., does it change known answer test values)? (If so, a version bump will be required from x.y.z to x.(y+1).0.)
• Does this PR change the list of algorithms available -- either adding, removing, or renaming? Does this PR otherwise change an API? (If so, PRs in fully supported downstream projects dependent on these, i.e., oqs-provider will also need to be ready for review and merge by the time this is merged.)

[baentsch]

Thanks @mkannwischer !

[bhess]

Thank you @mkannwischer !