Bump version in preparation for new tag (#10689)

https://github.com/flutter/flutter/issues/10688

VERSION

@@ -6,4 +6,4 @@
 # incompatible way, this version number might not change. Instead, the version
 # number for package:flutter will update to reflect that change.
 
-0.0.8-dev
+0.0.8

packages/flutter/pubspec.yaml

 name: flutter
-version: 0.0.28-dev
+version: 0.0.28
 author: Flutter Authors <flutter-dev@googlegroups.com>
 description: A framework for writing Flutter applications
 homepage: http://flutter.io

packages/flutter_driver/pubspec.yaml

 name: flutter_driver
-version: 0.0.6-dev
+version: 0.0.6
 description: Integration and performance test API for Flutter applications
 homepage: http://flutter.io
 author: Flutter Authors <flutter-dev@googlegroups.com>

packages/flutter_test/pubspec.yaml

 name: flutter_test
-version: 0.0.6-dev
+version: 0.0.6
 dependencies:
   # The flutter tools depend on very specific internal implementation
   # details of the 'test' package, which change between versions, so