Fix lints: unnecessary_brace_in_string_interp

pkg/analysis_server/lib/src/services/index/index.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 services.index;
 
 import 'dart:async';
 
 import 'package:analysis_server/src/provisional/index/index_core.dart';
 import 'package:analysis_server/src/services/index/indexable_element.dart';
@@ skipping 289 matching lines @@
 
   @override
   String toString() {
     String flagsStr = '';
     if (isQualified) {
       flagsStr += ' qualified';
     }
     if (isResolved) {
       flagsStr += ' resolved';
     }
-    return '[${offset} - ${(offset + length)}) $flagsStr in ${indexable}';
+    return '[$offset - ${offset + length}) $flagsStr in $indexable';
   }
 }
 
 /**
  * A [LocationImpl] with attached data.
  */
 class LocationWithData<D> extends LocationImpl {
   final D data;
 
   LocationWithData(LocationImpl location, this.data)
@@ skipping 41 matching lines @@
    */
   static RelationshipImpl getRelationship(String identifier) {
     RelationshipImpl relationship = _RELATIONSHIP_MAP[identifier];
     if (relationship == null) {
       relationship = new RelationshipImpl(identifier);
       _RELATIONSHIP_MAP[identifier] = relationship;
     }
     return relationship;
   }
 }