C++: Make QL-for-QL happy.

cpp/ql/lib/semmle/code/cpp/models/implementations/StdString.qll

@@ -15,18 +15,6 @@ private class StdBasicString extends ClassTemplateInstantiation {
   StdBasicString() { this.hasQualifiedName(["std", "bsl"], "basic_string") }
 }
 
-/**
- * The `std::basic_string::iterator` declaration.
- */
-private class StdBasicStringIterator extends Type instanceof Iterator {
-  StdBasicStringIterator() {
-    exists(Type unspecified |
-      unspecified.getEnclosingElement() = any(StdBasicString s).getTemplate() and
-      unspecified.getUnspecifiedType() = this
-    )
-  }
-}
-
 /**
  * A `std::string` function for which taint should be propagated.
  */