Tutorial: Extend literal include to contain full code changes in solution

The solution for step 7 todo 5 did not include all of the code changes.
Modify it to include the needed `#endif` code change.

Help/guide/tutorial/Adding System Introspection.rst

@@ -156,7 +156,7 @@ compute the square root in the ``mysqrt`` function. The ``mysqrt`` function in
   :name: MathFunctions/mysqrt.cxx-ifdef
   :language: c++
   :start-after: // if we have both log and exp then use them
-  :end-before: // do ten iterations
+  :end-before: return result;
 
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