Fix lints: unnecessary_brace_in_string_interp

pkg/analysis_server/test/integration/integration_tests.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 test.integration.analysis;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:convert';
 import 'dart:io';
@@ skipping 564 matching lines @@
       'id': id,
       'method': method
     };
     if (params != null) {
       command['params'] = params;
     }
     Completer completer = new Completer();
     _pendingCommands[id] = completer;
     String line = JSON.encode(command);
     _recordStdio('SEND: $line');
-    _process.stdin.add(UTF8.encoder.convert("${line}\n"));
+    _process.stdin.add(UTF8.encoder.convert("$line\n"));
     return completer.future;
   }
 
   /**
    * Start the server.  If [debugServer] is `true`, the server will be started
    * with "--debug", allowing a debugger to be attached. If [profileServer] is
    * `true`, the server will be started with "--observe" and
    * "--pause-isolates-on-exit", allowing the observatory to be used.
    */
   Future start(
@@ skipping 287 matching lines @@
   void populateMismatches(item, List<MismatchDescriber> mismatches);
 
   /**
    * Create a [MismatchDescriber] describing a mismatch with a simple string.
    */
   MismatchDescriber simpleDescription(String description) =>
       (Description mismatchDescription) {
         mismatchDescription.add(description);
       };
 }