Switch from homepage to repository in pubspec  (#687)

diff --git a/pubspec.yaml b/pubspec.yaml
index de21648..2689e46 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,7 +1,7 @@
 name: http
 version: 0.13.5-dev
-homepage: https://github.com/dart-lang/http
 description: A composable, multi-platform, Future-based API for HTTP requests.
+repository: https://github.com/dart-lang/http
 
 environment:
   sdk: '>=2.14.0 <3.0.0'