n-api: use Maybe version of Object::SetPrototype()

Fixes the following deprecation warning:

    ../src/node_api.cc:2020:30: warning: 'bool
    v8::Object::SetPrototype(v8::Local<v8::Value>)' is deprecated: Use
    maybe version [-Wdeprecated-declarations]
       wrapper->SetPrototype(proto);
    ../src/node_api.cc:2021:28: warning: 'bool
    v8::Object::SetPrototype(v8::Local<v8::Value>)' is deprecated: Use
    maybe version [-Wdeprecated-declarations]
       obj->SetPrototype(wrapper);

Backport-PR-URL: https://github.com/nodejs/node/pull/19447
PR-URL: https://github.com/nodejs/node/pull/14053


Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>