Update to the latest pkg:json_serializable

pkgs/pubspec_parse/.github/workflows/test-package.yml

diff --git a/pkgs/pubspec_parse/.github/workflows/test-package.yml b/pkgs/pubspec_parse/.github/workflows/test-package.yml
index df7aeb4..a818a1b 100644
--- a/pkgs/pubspec_parse/.github/workflows/test-package.yml
+++ b/pkgs/pubspec_parse/.github/workflows/test-package.yml
@@ -46,7 +46,7 @@
       fail-fast: false
       matrix:
         os: [ubuntu-latest]
-        sdk: [2.12.0, dev]
+        sdk: [2.14.0, dev]
     steps:
       - uses: actions/checkout@v2
       - uses: dart-lang/setup-dart@v1.0

pkgs/pubspec_parse/CHANGELOG.md

diff --git a/pkgs/pubspec_parse/CHANGELOG.md b/pkgs/pubspec_parse/CHANGELOG.md
index 9cc4b52..2601ee4 100644
--- a/pkgs/pubspec_parse/CHANGELOG.md
+++ b/pkgs/pubspec_parse/CHANGELOG.md
@@ -1,5 +1,7 @@
 ## 1.1.1-dev
 
+- Require Dart SDK >= 2.14.0
+
 ## 1.1.0
 
 - Export `HostedDetails` publicly.

pkgs/pubspec_parse/pubspec.yaml

diff --git a/pkgs/pubspec_parse/pubspec.yaml b/pkgs/pubspec_parse/pubspec.yaml
index 5e51c29..d19201e 100644
--- a/pkgs/pubspec_parse/pubspec.yaml
+++ b/pkgs/pubspec_parse/pubspec.yaml
@@ -6,19 +6,19 @@
 repository: https://github.com/dart-lang/pubspec_parse
 
 environment:
-  sdk: '>=2.12.0 <3.0.0'
+  sdk: '>=2.14.0 <3.0.0'
 
 dependencies:
   checked_yaml: ^2.0.1
   collection: ^1.15.0
-  json_annotation: ^4.1.0
+  json_annotation: ^4.3.0
   pub_semver: ^2.0.0
   yaml: ^3.0.0
 
 dev_dependencies:
   build_runner: ^2.0.3
   build_verify: ^2.0.0
-  json_serializable: ^5.0.0
+  json_serializable: ^6.0.0
   lints: ^1.0.0
   path: ^1.5.1
   # Needed because we are configuring `combining_builder`