Fixed type error.

templates/normal/experiment.cpp

@@ -34,8 +34,8 @@ auto calculate_hyperperiod() -> long long
 }
 }
 
 
 struct timestamps {
 struct timestamps {
-    cpp_time_base::duration start;
-    cpp_time_base::duration end;
+    cpp_time_base start;
+    cpp_time_base end;
     int core_id = 0;
     int core_id = 0;
 };
 };