src: fix warn_unused_result compiler warning

../src/node_file.cc:386:7: warning: ignoring return value of
function declared with 'warn_unused_result'
attribute [-Wunused-result]

PR-URL: https://github.com/nodejs/node/pull/32241
Refs: https://github.com/nodejs/node/pull/31972


Reviewed-By: Sam Roberts <vieuxtech@gmail.com>
Reviewed-By: David Carlier <devnexen@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>