C++: Fix test annotation for cpp/invalid-pointer-deref test

Author: jketema

cpp/ql/test/experimental/query-tests/Security/CWE/CWE-193/pointer-deref/test.cpp

@@ -369,7 +369,7 @@ void test26(unsigned size) {
   }
 
   if (p < end) {
-    int val = *p; // GOOD [FALSE POSITIVE]
+    int val = *p; // GOOD
   }
 }