Bump built_value from 8.2.3 to 8.3.0 in /jsonexample (#1241)

Bumps [built_value](https://github.com/google/built_value.dart) from 8.2.3 to 8.3.0.
- [Release notes](https://github.com/google/built_value.dart/releases)
- [Changelog](https://github.com/google/built_value.dart/blob/master/CHANGELOG.md)
- [Commits](https://github.com/google/built_value.dart/compare/v8.2.3...v8.3.0)

---
updated-dependencies:
- dependency-name: built_value
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

jsonexample/pubspec.lock

@@ -91,7 +91,7 @@ packages:
       name: built_value
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "8.2.3"
+    version: "8.3.0"
   built_value_generator:
     dependency: "direct dev"
     description:

jsonexample/pubspec.yaml

@@ -8,7 +8,7 @@ environment:
 dependencies:
   json_annotation: ^4.5.0
   built_collection: ^5.0.0
-  built_value: ^8.2.3
+  built_value: ^8.3.0
 
   flutter:
     sdk: flutter