Deprecate the generated element library and clean up imports

pkg/analysis_server/lib/src/computer/computer_hover.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 computer.hover;
 
 import 'package:analysis_server/plugin/protocol/protocol.dart'
     show HoverInformation;
 import 'package:analysis_server/src/computer/computer_overrides.dart';
 import 'package:analysis_server/src/utilities/documentation.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/src/generated/ast.dart';
-import 'package:analyzer/src/generated/element.dart';
 
 /**
  * A computer for the hover at the specified offset of a Dart [CompilationUnit].
  */
 class DartUnitHoverComputer {
   final CompilationUnit _unit;
   final int _offset;
 
   DartUnitHoverComputer(this._unit, this._offset);
 
@@ skipping 81 matching lines @@
         Element interfaceClass = superElement.enclosingElement;
         return removeDartDocDelimiters(rawDoc) +
             '\n\nCopied from `${interfaceClass.displayName}`.';
       }
     }
     return null;
   }
 
   static _safeToString(obj) => obj != null ? obj.toString() : null;
 }