Prepare to release v3.2.0 (#716)

CHANGELOG.md

diff --git a/CHANGELOG.md b/CHANGELOG.md
index c8b4fd2..00448bd 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,4 +1,4 @@
-#### 3.2.0-dev
+#### 3.2.0
 
   * Deprecate `Optional`. With the introduction of non-null by default in Dart
     SDK 2.12, existing users should migrate to non-nullable types. This type

pubspec.yaml

diff --git a/pubspec.yaml b/pubspec.yaml
index 7595268..6759137 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -3,7 +3,7 @@
   Quiver is a set of utility libraries for Dart that makes using many Dart
   libraries easier and more convenient, or adds additional functionality.
 repository: https://github.com/google/quiver-dart
-version: 3.2.0-dev
+version: 3.2.0
 
 # When updating SDK lower bound, also update .github/workflows/dart.yml to test
 # against the new lower bound.