Remove more libraries directives from server

pkg/analysis_server/lib/src/collections.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 collections;
-
 /**
  * Returns the concatenation of the input [iterables].
  *
  * The returned iterable is a lazily-evaluated view on the input iterables.
  */
 Iterable/*<E>*/ concat/*<E>*/(Iterable<Iterable/*<E>*/ > iterables) =>
     iterables.expand((x) => x);
 
 /**
  * Returns the concatenation of the input [iterables] as a [List].
@@ skipping 23 matching lines @@
 
   int get hashCode => first.hashCode ^ last.hashCode;
 
   bool operator ==(other) {
     if (other is! Pair) return false;
     return other.first == first && other.last == last;
   }
 
   String toString() => '($first, $last)';
 }