Remove references to not-exiting-anymore FrozenHashCodeException.

pkg/analyzer/lib/src/dart/element/element.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library analyzer.src.dart.element.element;
 
 import 'dart:collection';
 import 'dart:math' show min;
 
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 2727 matching lines @@
   void set documentationComment(String doc) {
     assert(!isResynthesized);
     _docComment = doc?.replaceAll('\r\n', '\n');
   }
 
   @override
   Element get enclosingElement => _enclosingElement;
 
   /**
    * Set the enclosing element of this element to the given [element].
-   *
-   * Throws [FrozenHashCodeException] if the hashCode can't be changed.
    */
   void set enclosingElement(Element element) {
     _enclosingElement = element as ElementImpl;
   }
 
   /**
    * Return the enclosing unit element (which might be the same as `this`), or
    * `null` if this element is not contained in any compilation unit.
    */
   CompilationUnitElementImpl get enclosingUnit {
@@ skipping 128 matching lines @@
   void set metadata(List<ElementAnnotation> metadata) {
     assert(!isResynthesized);
     _metadata = metadata;
   }
 
   @override
   String get name => _name;
 
   /**
    * Changes the name of this element.
-   *
-   * Throws [FrozenHashCodeException] if the hashCode can't be changed.
    */
   void set name(String name) {
     this._name = name;
   }
 
   @override
   int get nameLength => displayName != null ? displayName.length : 0;
 
   @override
   int get nameOffset => _nameOffset;
 
   /**
    * Sets the offset of the name of this element in the file that contains the
    * declaration of this element.
-   *
-   * Throws [FrozenHashCodeException] if the hashCode can't be changed.
    */
   void set nameOffset(int offset) {
     _nameOffset = offset;
   }
 
   @override
   Source get source {
     if (_enclosingElement == null) {
       return null;
     }
@@ skipping 5952 matching lines @@
 
   @override
   DartObject computeConstantValue() => null;
 
   @override
   void visitChildren(ElementVisitor visitor) {
     super.visitChildren(visitor);
     _initializer?.accept(visitor);
   }
 }