src: fix compiler warning in async_wrap.cc

    ../src/async_wrap.cc: In function ‘uint16_t node::ToAsyncHooksType(v8::PromiseHookType)’:
    ../src/async_wrap.cc:313:1: error: control reaches end of non-void function [-Werror=return-type]
     }

Refs: https://github.com/nodejs/node/pull/32891

PR-URL: https://github.com/nodejs/node/pull/33322


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>