Bump to 6.0.0 (dart-lang/markdown#443)

pkgs/markdown/CHANGELOG.md

diff --git a/pkgs/markdown/CHANGELOG.md b/pkgs/markdown/CHANGELOG.md
index 0072bcb..9742ee2 100644
--- a/pkgs/markdown/CHANGELOG.md
+++ b/pkgs/markdown/CHANGELOG.md
@@ -1,4 +1,4 @@
-## 6.0.0-dev
+## 6.0.0
 
 * Require Dart 2.17
 * Add support to GFM extension for GitHub task lists (aka checkboxes).  These

pkgs/markdown/lib/src/version.dart

diff --git a/pkgs/markdown/lib/src/version.dart b/pkgs/markdown/lib/src/version.dart
index 92964be..0773426 100644
--- a/pkgs/markdown/lib/src/version.dart
+++ b/pkgs/markdown/lib/src/version.dart
@@ -1,2 +1,2 @@
 // Generated code. Do not modify.
-const packageVersion = '6.0.0-dev';
+const packageVersion = '6.0.0';

pkgs/markdown/pubspec.yaml

diff --git a/pkgs/markdown/pubspec.yaml b/pkgs/markdown/pubspec.yaml
index 0dc576f..4a69ba5 100644
--- a/pkgs/markdown/pubspec.yaml
+++ b/pkgs/markdown/pubspec.yaml
@@ -1,5 +1,5 @@
 name: markdown
-version: 6.0.0-dev
+version: 6.0.0
 
 description: A portable Markdown library written in Dart that can parse
  Markdown into HTML.