Update @actions/cache version to 1.0.8

**Description:**
The action depends on [`@actions/cache`](https://github.com/ruby/setup-ruby/blob/f20f1eae726df008313d2e0d78c5e602562a1bcf/package.json#L25). The latest version `1.0.8` is now available and it supports upto 10GB cache upload. 

**Justification:**
Support 10GB cache upload using the latest version `1.0.8` of [`@actions/cache` ](https://www.npmjs.com/package/@actions/cache)
