Remove remaining references to defunct parameter `--failure-summary`.

pkg/front_end/test/fasta/testing.json

 {
 "":"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.md file.",
 
   "packages": "../../../../.packages",
 
   "suites": [
 
     {
@@ skipping 136 matching lines @@
         "/sdk/tests/language/regress_23996_test\\.dart$",
         "/sdk/tests/language/round_test\\.dart$"
       ]
     },
 
     {
       "name": "dart2js",
       "kind": "test_dart",
       "arch": "x64",
       "mode": "release",
-      "common": "--dart2js-batch --time -pcolor --report --failure-summary -ax64 -mrelease",
+      "common": "--dart2js-batch --time -pcolor --report -ax64 -mrelease",
       "command-lines": [
         "--checked dart2js",
         "-cdart2js -rd8 --exclude-suite=observatory_ui",
         "-cdart2js -rd8 dart2js_extra dart2js_native"
       ]
     }
   ],
 
   "analyze": {
 
@@ skipping 18 matching lines @@
       "^pkg/compiler/lib/src/elements/modelx\\.dart",
       "^pkg/compiler/lib/src/js_backend/namer\\.dart",
       "^pkg/compiler/lib/src/resolution/members\\.dart",
       "^pkg/compiler/lib/src/resolution/resolution\\.dart",
       "^pkg/compiler/lib/src/resolution/resolution_strategy\\.dart",
       "^pkg/compiler/lib/src/serialization/equivalence\\.dart",
       "^pkg/compiler/lib/src/serialization/resolved_ast_serialization\\.dart"
     ]
   }
 }