Allow null-safe json_annotation (dart-lang/pubspec_parse#61)

prepare to release v0.1.6
diff --git a/pkgs/pubspec_parse/CHANGELOG.md b/pkgs/pubspec_parse/CHANGELOG.md
index 7e74a55..f7a1a3a 100644
--- a/pkgs/pubspec_parse/CHANGELOG.md
+++ b/pkgs/pubspec_parse/CHANGELOG.md
@@ -1,6 +1,7 @@
-## 0.1.6-dev
+## 0.1.6
 
 - Update SDK requirement to `>=2.7.0 <3.0.0`.
+- Allow `package:json_annotation` `v4.x`.
 
 ## 0.1.5
 
diff --git a/pkgs/pubspec_parse/pubspec.yaml b/pkgs/pubspec_parse/pubspec.yaml
index 09d2fb9..6e2a7e9 100644
--- a/pkgs/pubspec_parse/pubspec.yaml
+++ b/pkgs/pubspec_parse/pubspec.yaml
@@ -2,8 +2,8 @@
 description: >-
   Simple package for parsing pubspec.yaml files with a type-safe API and rich
   error reporting.
-version: 0.1.6-dev
-homepage: https://github.com/dart-lang/pubspec_parse
+version: 0.1.6
+repository: https://github.com/dart-lang/pubspec_parse
 
 environment:
   sdk: '>=2.7.0 <3.0.0'
@@ -11,7 +11,7 @@
 dependencies:
   checked_yaml: ^1.0.0
   # Verified that no new features since 1.0.0 are used - be careful!
-  json_annotation: '>=1.0.0 <4.0.0'
+  json_annotation: '>=1.0.0 <5.0.0'
   pub_semver: ^1.3.2
   yaml: ^2.1.12