Update C++ variable hiding test

Structured bindings are now handled better, so the false negative
related to structured bindings is now a true positive.

Author: jketema

cpp/ql/test/query-tests/Best Practices/Hiding/DeclarationHidesVariable/DeclarationHidesVariable.expected

@@ -1,2 +1,3 @@
 | hiding.cpp:6:17:6:17 | i | Variable i hides another variable of the same name (on $@). | hiding.cpp:4:13:4:13 | i | line 4 |
 | hiding.cpp:18:15:18:15 | k | Variable k hides another variable of the same name (on $@). | hiding.cpp:15:11:15:11 | k | line 15 |
+| hiding.cpp:38:11:38:11 | x | Variable x hides another variable of the same name (on $@). | hiding.cpp:36:9:36:9 | x | line 36 |

cpp/ql/test/query-tests/Best Practices/Hiding/DeclarationHidesVariable/hiding.cpp

@@ -35,7 +35,7 @@ void structuredBinding() {
   int xs[1] = {1};
   auto [x] = xs;
   {
-    auto [x] = xs; // BAD [NOT DETECTED]
+    auto [x] = xs; // BAD
     auto [y] = xs; // GOOD
   }
 }