chore(deps): remove unused coverage dev dependency (#125)

diff --git a/pubspec.yaml b/pubspec.yaml
index 5cd5ecd..70f228b 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -14,5 +14,4 @@
   meta: ^1.3.0
 
 dev_dependencies:
-  coverage: ^0.14.2
   test: ^1.16.0