src: remove unused locale.h

This commit removes the locale.h header as it does not look like it is
used.

PR-URL: https://github.com/nodejs/node/pull/23120


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>