Don't include unistd.h

It's not needed.

src/dump.c

@@ -9,7 +9,6 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <unistd.h>
 
 #include <jansson.h>
 #include "strbuffer.h"

src/load.c

@@ -12,7 +12,6 @@
 #include <stdlib.h>
 #include <string.h>
 #include <stdarg.h>
-#include <unistd.h>
 #include <assert.h>
 
 #include <jansson.h>