Prepare to release v4.0.0-nullsafety.0 (#770)

Closes #763

Author: kevmoo

json_serializable/CHANGELOG.md

@@ -1,10 +1,10 @@
-## 4.0.0-nullsafety.1
+## 4.0.0-nullsafety.0
 
 - Generates null-safe code.
   - The `nullable` field on `JsonKey` ignored. The nullability of a field is now 
     determined by the Dart type system.
 - **BREAKING** `bool defaultProvided` arg added to `TypeHelper.deserialize`.
-  *Only applies to folks using `TypeHelper` directly.*
+  *Only applies to code using `TypeHelper` directly.*
 
 ## 3.5.1
 

json_serializable/pubspec.yaml

@@ -1,5 +1,5 @@
 name: json_serializable
-version: 4.0.0-nullsafety.1
+version: 4.0.0-nullsafety.0
 description: >-
   Automatically generate code for converting to and from JSON by annotating
   Dart classes.
@@ -16,7 +16,7 @@ dependencies:
   # `json_annotation` properly constrains all features it provides.
   # For v3 only – allow a wide range since the only change was to REMOVE things
   # from json_annotation
-  json_annotation: '>=3.1.0 <3.2.0'
+  json_annotation: '>=4.0.0-nullsafety.0 <4.1.0'
   meta: ^1.3.0-nullsafety.5
   path: ^1.8.0-nullsafety.2
   source_gen: ^0.9.6
@@ -32,10 +32,3 @@ dev_dependencies:
   stack_trace: ^1.10.0-nullsafety.5
   test: ^1.16.0-nullsafety.7
   yaml: ^3.0.0-nullsafety.0
-
-dependency_overrides:
-  json_annotation:
-    path: ../json_annotation
-
-  # For yaml!
-  yaml: 3.0.0-nullsafety.0