Use std::variant instead of mapbox::util::variant (#6903)

src/benchmarks/json_render.cpp

@@ -86,7 +86,7 @@ json::Object load(const char *filename)
 
     json::Value result;
     convert(document, result);
-    return result.get<json::Object>();
+    return std::get<json::Object>(result);
 }
 
 } // namespace

src/benchmarks/match.cpp

@@ -232,9 +232,9 @@ try
         {
             engine::api::ResultT result = json::Object();
             const auto rc = osrm.Match(params, result);
-            auto &json_result = result.get<json::Object>();
+            auto &json_result = std::get<json::Object>(result);
             if (rc != Status::Ok ||
-                json_result.values.at("matchings").get<json::Array>().values.size() != 1)
+                std::get<json::Array>(json_result.values.at("matchings")).values.size() != 1)
             {
                 throw std::runtime_error{"Couldn't match"};
             }

src/benchmarks/route.cpp

@@ -76,7 +76,7 @@ try
         {
             engine::api::ResultT result = json::Object();
             const auto rc = osrm.Route(params, result);
-            auto &json_result = result.get<json::Object>();
+            auto &json_result = std::get<json::Object>(result);
             if (rc != Status::Ok || json_result.values.find("routes") == json_result.values.end())
             {
                 throw std::runtime_error{"Couldn't route"};