Remove deprecated_warning.

pkg/front_end/lib/src/fasta/kernel/fasta_accessors.dart

 // Copyright (c) 2016, 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 fasta.fasta_accessors;
 
 import 'package:kernel/ast.dart'
     hide InvalidExpression, InvalidInitializer, InvalidStatement;
 
 import '../../scanner/token.dart' show Token;
@@ skipping 107 matching lines @@
 
   Expression buildMethodInvocation(
       Expression receiver, Name name, Arguments arguments, int offset,
       {bool isConstantExpression, bool isNullAware, bool isImplicitCall});
 
   DartType validatedTypeVariableUse(
       TypeParameterType type, int offset, bool nonInstanceAccessIsError);
 
   void warning(Message message, int charOffset);
 
-  void deprecated_warning(String message, [int charOffset]);
-
   void warnUnresolvedSuperGet(Name name, int charOffset);
 
   void warnUnresolvedSuperSet(Name name, int charOffset);
 
   void warnUnresolvedSuperMethod(Name name, int charOffset);
 }
 
 abstract class FastaAccessor implements Accessor {
   BuilderHelper get helper;
 
@@ skipping 918 matching lines @@
     offset ??= offsetForToken(this.token);
     return helper.throwNoSuchMethodError(new NullLiteral()..fileOffset = offset,
         plainNameForRead, arguments, offset,
         isGetter: isGetter, isSetter: isSetter);
   }
 }
 
 bool isFieldOrGetter(Member member) {
   return member is Field || (member is Procedure && member.isGetter);
 }