remove unneeded header

include/llarp/string.h

@@ -1,19 +0,0 @@
-#ifndef LLARP_STRING_H
-#define LLARP_STRING_H
-
-#include <util/common.hpp>
-
-#ifndef __FreeBSD__
-#if !(__APPLE__ && __MACH__)
-size_t INLINE
-strnlen(const char* str, size_t sz)
-{
-  size_t slen = 0;
-  while (sz-- && str[slen])
-    slen++;
-  return slen;
-}
-#endif
-#endif
-
-#endif