trivial: Move a code comment (//...) to the line above the code

This matches the way the previous, related code example is written,
a fact you can observe more readily by reviewing the patch of this
commit with larger context:

    git diff -U19

Specifically, the previous example looks like this:

    // bad: the number of elements is not passed to f()
    f(new int[n]);

Author: mfwitten

CppCoreGuidelines.md

@@ -767,7 +767,8 @@ We can of course pass the number of elements along with the pointer:
 
     void g2(int n)
     {
-        f2(new int[n], n);  // bad: a wrong number of elements can be passed to f2()
+        // bad: a wrong number of elements can be passed to f2()
+        f2(new int[n], n);
     }
 
 Passing the number of elements as an argument is better (and far more common) than just passing the pointer and relying on some (unstated) convention for knowing or discovering the number of elements. However (as shown), a simple typo can introduce a serious error. The connection between the two arguments of `f2()` is conventional, rather than explicit.