Increase the pubspec version (dart-lang/pub_semver#30)

I meant to do this in the last PR.

pkgs/pub_semver/pubspec.yaml

diff --git a/pkgs/pub_semver/pubspec.yaml b/pkgs/pub_semver/pubspec.yaml
index a537788..ec526bf 100644
--- a/pkgs/pub_semver/pubspec.yaml
+++ b/pkgs/pub_semver/pubspec.yaml
@@ -1,5 +1,5 @@
 name: pub_semver
-version: 1.4.0
+version: 1.4.1
 author: Dart Team <misc@dartlang.org>
 description: >
  Versions and version constraints implementing pub's versioning policy. This