Bump use of pkg/args to <2.0.0. (#644)

diff --git a/pubspec.yaml b/pubspec.yaml
index 6d4b3e5..a9ac7d1 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -8,7 +8,7 @@
   sdk: ">=1.8.0 <2.0.0"
 dependencies:
   analyzer: '^0.30.0'
-  args: '>=0.12.1 <0.14.0'
+  args: '>=0.12.1 <2.0.0'
   path: '>=1.0.0 <2.0.0'
   source_span: '>=1.4.0 <2.0.0'
 dev_dependencies: