n-api: simplify uv_idle wrangling

uv_idle_init(), uv_idle_start() and uv_idle_stop() always succeed.
Remove the superfluous error handling.

Refs: https://github.com/libuv/libuv/pull/2803

PR-URL: https://github.com/nodejs/node/pull/32997


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: David Carlier <devnexen@gmail.com>
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Juan José Arboleda <soyjuanarbol@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>