Update to node16

Node 12 has an end of life on April 30, 2022.

This PR updates the default runtime to [node16](https://github.blog/changelog/2021-12-10-github-actions-github-hosted-runners-now-run-node-js-16-by-default/), rather then node12. 

This is supported on all Actions Runners v2.285.0 or later.

action.yml

@@ -18,7 +18,7 @@ outputs:
   cache-hit:
     description: 'A boolean value to indicate an exact match was found for the primary key'
 runs:
-  using: 'node12'
+  using: 'node16'
   main: 'dist/restore/index.js'
   post: 'dist/save/index.js'
   post-if: 'success()'