Fix style issue

Author: benjie

CONTRIBUTING.md

@@ -152,7 +152,7 @@ Once it's ready for review, please [open a pull request](https://github.com/grap
 
 ### Add a blog post
 
-This repository holds the [graphql.org blog](https://graphql.org/blog/) at [source/src/pages/blog](https://github.com/graphql/graphql.github.io/tree/source/src/pages/blog). Blog posts may contain announcements, news, best practices and more.  
+This repository holds the [graphql.org blog](https://graphql.org/blog/) at [source/src/pages/blog](https://github.com/graphql/graphql.github.io/tree/source/src/pages/blog). Blog posts may contain announcements, news, best practices and more.
 
 Contributions are very welcome!