Make Call a subclass of ExprParent. All of its subclasses are in any case (via Expr or Stmt)

Author: smowton

java/ql/src/semmle/code/java/Expr.qll

@@ -1808,7 +1808,7 @@ class WildcardTypeAccess extends Expr, @wildcardtypeaccess {
  * This includes method calls, constructor and super constructor invocations,
  * and constructors invoked through class instantiation.
  */
-class Call extends Top, @caller {
+class Call extends ExprParent, @caller {
   /** Gets an argument supplied in this call. */
   /*abstract*/ Expr getAnArgument() { none() }