Fix homepage URL (dart-lang/source_maps#43)

pkgs/source_maps/pubspec.yaml

diff --git a/pkgs/source_maps/pubspec.yaml b/pkgs/source_maps/pubspec.yaml
index 3c42700..f2db1eb 100644
--- a/pkgs/source_maps/pubspec.yaml
+++ b/pkgs/source_maps/pubspec.yaml
@@ -2,7 +2,7 @@
 version: 0.10.9-dev
 
 description: Library to programmatically manipulate source map files.
-homepage: http://github.com/dart-lang/source_maps
+homepage: https://github.com/dart-lang/source_maps
 
 environment:
   sdk: '>=2.0.0 <3.0.0'