Drop git dependency override (#180)

diff --git a/pubspec.yaml b/pubspec.yaml
index 7123e28..f092d9f 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -17,17 +17,3 @@
   test: any
   test_api: any
   test_core: any
-
-dependency_overrides:
-  test_api:
-    git:
-      url: https://github.com/dart-lang/test.git
-      path: pkgs/test_api
-  test_core:
-    git:
-      url: git://github.com/dart-lang/test
-      path: pkgs/test_core
-  test:
-    git:
-      url: git://github.com/dart-lang/test
-      path: pkgs/test