docs: min action version v6.7.9 needed for caching (#1474)

Author: MikeMcC399

CHANGELOG.md

@@ -9,6 +9,7 @@ See [Releases](https://github.com/cypress-io/github-action/releases) for full de
 | v6.9.0  | Add parameter validation for `command`                                                                       |
 | v6.8.0  | Examples remove Node.js 18. End of support for Node.js 18.                                                   |
 | v6.7.10 | Examples updated to Cypress 14                                                                               |
+| v6.7.9  | Migrate to @actions/cache@4.0.0 for continued access to GitHub Actions caching services                      |
 | v6.7.0  | Examples remove Node.js 21. End of support for Node.js 21.                                                   |
 | v6.6.0  | Add parameter `summary-title`                                                                                |
 | v6.5.0  | Examples remove Node.js 16. End of support for Node.js 16.                                                   |

README.md

@@ -1831,6 +1831,7 @@ View the [CHANGELOG](./CHANGELOG.md) document for an overview of version changes
 ## Compatibility
 
 - `github-action@v6` is the current recommended version, uses `node20` and is compatible with Cypress `10` and above.
+- `[email protected]` is the minimum version required to use GitHub Actions caching services. The legacy caching service used by lower versions of the action is no longer available.
 - `github-action` versions `v1` to `v5` are unsupported: they rely on Node.js `12` and `16` in End-of-life status.
 
 ## Contributing