src: remove <unistd.h> from node_os.cc

The file does not use sysconf() and its use of gethostname() has been
removed, so including <unistd.h> appears to be unnecessary.

PR-URL: https://github.com/nodejs/node/pull/44668
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Jiawen Geng <technicalcute@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

src/node_os.cc

@@ -28,7 +28,6 @@
 #endif  // __MINGW32__
 
 #ifdef __POSIX__
-# include <unistd.h>        // gethostname, sysconf
 # include <climits>         // PATH_MAX on Solaris.
 #endif  // __POSIX__