Fix realloc bug in static_format

src/format.hpp

@@ -270,7 +270,6 @@ std::string_view static_format(ArenaAllocator &arena, Ts &&...ts) {
   char *buf = result;
   (detail::term(ts).write(buf), ...);
   const int size = static_cast<int>(buf - result);
-  return std::string_view(
-      arena.realloc(result, upper_bound, upper_bound - size),
+  return std::string_view(arena.realloc(result, upper_bound, size),
                           static_cast<std::size_t>(size));
 }