Corrected markdown for example code (#30387)

The markdown used in the examples in the section titled Implementation had the closing back-ticks specified on the wrong line, causing the code examples to be incorrectly displayed.

guide/english/cplusplus/for-loop/index.md

@@ -59,8 +59,7 @@ The update statement is used to alter the loop variable by using simple operatio
 
 You will often see an increment operation as the update statement (e.g. i++, count++). This is often seen as one of the distinguishing features and possible name sources for the C++ language.
 
-## IMPLEMENTATION:
-
+## Implementation
 ```C++
 #include <iostream>
 using std::cout; // Here we use the scope resolution operator to define the scope of the standard functions as std
@@ -103,7 +102,6 @@ The body of the for loop need not be enclosed in braces if the loop iterates ove
    for( int a = 10; a < 20; a++ ) 
       cout << "value of a: " << a << endl;
 
-
    return 0;
 }
 ```