src: prefer make_unique

In most of the code base we use make_unique instead of
new unique_ptr. Update node_platform.cc to be consistent
with that.

Signed-off-by: Michael Dawson <michael_dawson@ca.ibm.com>

PR-URL: https://github.com/nodejs/node/pull/33378


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Zeyu Yang <himself65@outlook.com>
Reviewed-By: Juan José Arboleda <soyjuanarbol@gmail.com>