tests : remove json.hpp from a test (#13880)

ggml-ci

tests/test-chat-parser.cpp

@@ -7,7 +7,6 @@
 //
 #include <exception>
 #include <iostream>
-#include <json.hpp>
 #include <string>
 
 #include "chat-parser.h"
@@ -15,8 +14,6 @@
 #include "log.h"
 #include "regex-partial.h"
 
-using json = nlohmann::ordered_json;
-
 template <class T>
 static void assert_equals(const T & expected, const T & actual) {
     if (expected != actual) {