Bump version to 2.2 (flutter#247)

Author: rami-a

gallery/gallery/pubspec.yaml

@@ -1,7 +1,7 @@
 name: gallery
 description: A resource to help developers evaluate and use Flutter.
 
-version: 2.1.0+020100
+version: 2.2.0+020200
 
 environment:
   sdk: ">=2.3.0 <3.0.0"