docs: update ci-build-caching (#41763)

This tiny PR is just to update document in [Continuous Integration (CI) Build Caching - GitHub Actions](https://nextjs.org/docs/advanced-features/ci-build-caching#github-actions).

The last version of `actions/cache@v2` is almost an year old, which is [2.1.7](https://github.com/actions/cache/releases/tag/v2.1.7).
It also uses [`::set-output` which is now deprecated](https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/), and users should start moving to `actions/cache@v3` instead.


As stated in [GitHub Actions: Deprecating save-state and set-output commands](https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/), the deprecated method will be fully disable them on 31st May 2023, which we still have times to move.

docs/advanced-features/ci-build-caching.md

@@ -75,7 +75,7 @@ cache:
 Using GitHub's [actions/cache](https://github.com/actions/cache), add the following step in your workflow file:
 
 ```yaml
-uses: actions/cache@v2
+uses: actions/cache@v3
 with:
   # See here for caching with `yarn` https://github.com/actions/cache/blob/main/examples.md#node---yarn or you can leverage caching with actions/setup-node https://github.com/actions/setup-node
   path: |