Apply fixes on recent class element tests

Ref https://github.com/tc39/test262/pull/1711#issuecomment-419973158

src/class-elements/grammar-special-meth-ctor-set.case

@@ -12,4 +12,4 @@ template: syntax/invalid
 ---*/
 
 //- elements
-set constructor() {}
+set constructor(_) {}

src/class-elements/grammar-static-ctor-accessor-meth-valid.case

@@ -17,7 +17,7 @@ template: syntax/valid
 
 //- elements
 static get constructor() {}
-static set constructor() {}
+static set constructor(_) {}
 constructor() {} // stacks with a valid constructor
 //- teardown
 assert(C.hasOwnProperty('constructor'));

src/class-elements/grammar-static-private-ctor-meth-valid.case

-// Copyright (C) 2018 Leo Balter. All rights reserved.
-// This code is governed by the BSD license found in the LICENSE file.
-
-/*---
-desc: Static Methods can be named constructor
-info: |
-    Class Definitions / Static Semantics: Early Errors
-
-    ClassElement : static MethodDefinition
-        It is a Syntax Error if PropName of MethodDefinition is "prototype"
-template: syntax/invalid
----*/
-
-//- elements
-static constructor() {}
-constructor() {} // stacks with a valid constructor

src/class-elements/grammar-static-set-meth-prototype.case

@@ -12,4 +12,4 @@ template: syntax/invalid
 ---*/
 
 //- elements
-static set prototype() {}
+static set prototype(_) {}