chore: upgrade to actions/cache v4 (GitHub is closing down our existing actions/cache)

[lauthieb]

Changes description

Following Decathlon + GitHub recommendations, I have to do this quick PR even if the project is no longer maintained.

TL;DR: GitHub actions/cache@v1-v2 is closing down. So we just need to move to actions/cache@v4:

Checklist

• Make sure you are requesting to pull a topic/feature/bugfix branch. Please, don't request directly from your main!
• Check commits & PR names matches our requested structure. It must follow the https://www.conventionalcommits.org pattern.
• Check your code additions will fail neither code linting checks.
• I have reviewed the submitted code.
• I have tested on related showcases.
• If it includes design changes, please ask for a review design-system-core-team-design GitHub team.

Does this introduce a breaking change?

• No