doc: add change info for async_hooks.executionAsyncId()

Add meta information to async_hooks documentation informing that
executionAsyncId was renamed from currentId at Node.js 8.2.0.

PR-URL: https://github.com/nodejs/node/pull/17813


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ali Ijaz Sheikh <ofrobots@google.com>