Bump the version to 1.3.2.

This was supposed to happen in the last CL, but didn't instead.

R=sigmund@google.com

Review URL: https://codereview.chromium.org//1971573002 .
diff --git a/pubspec.yaml b/pubspec.yaml
index 8410e05..3e87e2b 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: stream_channel
-version: 1.3.1
+version: 1.3.2
 description: An abstraction for two-way communication channels.
 author: Dart Team <misc@dartlang.org>
 homepage: https://github.com/dart-lang/stream_channel