pg_upgrade: remove redundant include files

The files were already included by pg_upgrade.h.

Author: bmomjian

contrib/pg_upgrade/exec.c

@@ -12,7 +12,6 @@
 #include "pg_upgrade.h"
 
 #include <fcntl.h>
-#include <unistd.h>
 #include <sys/types.h>
 
 static void check_data_dir(const char *pg_data);

contrib/pg_upgrade/option.c

@@ -16,7 +16,6 @@
 
 #include <time.h>
 #include <sys/types.h>
-#include <sys/stat.h>
 #ifdef WIN32
 #include <io.h>
 #endif