Fix code in c++ (#4373)

src/data/roadmaps/cpp/content/110-stl/103-date-time.md

@@ -19,7 +19,7 @@ A `duration` represents a span of time, which can be expressed in various units
 int main() {
     std::chrono::seconds sec(5);
     std::chrono::minutes min(2);
-    std(chrono)::hours hr(1);
+    std::chrono::hours hr(1);
     return 0;
 }
 ```
@@ -87,4 +87,4 @@ int main() {
 }
 ```
 
-This summarizes the basic functionality of working with date and time in C++ using the `chrono` library. You can find more advanced features, such as casting durations and time arithmetic, in the [C++ reference](https://en.cppreference.com/w/cpp/chrono).
+This summarizes the basic functionality of working with date and time in C++ using the `chrono` library. You can find more advanced features, such as casting durations and time arithmetic, in the [C++ reference](https://en.cppreference.com/w/cpp/chrono).