Delete the msdn reference in NestedLoopSameVar

It was a Visual Basic reference anyway, and it doesn't seem to provide more information than the link we have already.

Author: MathiasVP

cpp/ql/src/Likely Bugs/NestedLoopSameVar.qhelp

@@ -25,9 +25,6 @@ outer loop. </p>
 <li>
   Tutorialspoint - The C++ Programming Language: <a href="http://www.tutorialspoint.com/cplusplus/cpp_nested_loops.htm">C++ nested loops</a>
 </li>
-<li>
-  MSDN Library: <a href="https://docs.microsoft.com/en-us/dotnet/visual-basic/programming-guide/language-features/control-flow/nested-control-structures">Nested Control Structures</a>
-</li>