src: remove outdated `Neuter()` call in `node_buffer.cc`

This call was introduced in 827ee498 to avoid a crash in a
later `Neuter()` call that has later been removed in ebbbc5a7,
rendering the original call unnecessary.

Refs: https://github.com/nodejs/node/pull/3624
Refs: https://github.com/nodejs/node/pull/5204

PR-URL: https://github.com/nodejs/node/pull/25479


Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>