update typed_data dep (#149)

diff --git a/pubspec.yaml b/pubspec.yaml
index 500c527..d9f2508 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -60,4 +60,5 @@
     git:
       url: git://github.com/dart-lang/test.git
       path: pkgs/test
-  typed_data: 1.3.0-nullsafety
+  typed_data:
+    git: git://github.com/dart-lang/typed_data.git