Update Firefox status for Dart 2

Cq-Include-Trybots: luci.dart.try: dart2js-strong-linux-x64-ff-try, dart2js-strong-win-x64-ff-try
Change-Id: I9e04c74fc44976488cacad5b73036c0c8487462e
Reviewed-on: https://dart-review.googlesource.com/64543
Reviewed-by: Sigmund Cherem <sigmund@google.com>
Reviewed-by: William Hesse <whesse@google.com>
Commit-Queue: William Hesse <whesse@google.com>
diff --git a/tests/language_2/language_2_dart2js.status b/tests/language_2/language_2_dart2js.status
index 4a641cd..ac59215 100644
--- a/tests/language_2/language_2_dart2js.status
+++ b/tests/language_2/language_2_dart2js.status
@@ -48,9 +48,6 @@
 field_type_check2_test/01: MissingRuntimeError
 round_test: Pass, Fail, OK # Fixed in ff 35. Common JavaScript engine Math.round bug.
 
-[ $compiler == dart2js && $runtime == ff && $strong ]
-call_function_test: RuntimeError
-
 [ $compiler == dart2js && $runtime == jsshell ]
 async_call_test: RuntimeError # Timer interface not supported: Issue 7728.
 async_star_await_pauses_test: RuntimeError # Need triage