bump build_runner dep dependency (dart-lang/pubspec_parse#70)

pkgs/pubspec_parse/pubspec.yaml

diff --git a/pkgs/pubspec_parse/pubspec.yaml b/pkgs/pubspec_parse/pubspec.yaml
index 469e004..c5577b0 100644
--- a/pkgs/pubspec_parse/pubspec.yaml
+++ b/pkgs/pubspec_parse/pubspec.yaml
@@ -16,7 +16,7 @@
   yaml: ^3.0.0
 
 dev_dependencies:
-  build_runner: ^1.0.0
+  build_runner: ^2.0.3
   build_verify: ^2.0.0
   json_serializable: ^4.0.2
   path: ^1.5.1