Remove unnecessary dependency override (#12)

diff --git a/pubspec.yaml b/pubspec.yaml
index 919d5d0..e9eca30 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -28,5 +28,3 @@
       url: https://github.com/dart-lang/test.git
       ref: drop-package-resolver
       path: pkgs/test
-  package_config: ^1.9.1
-