docs: removed deprecated url

Author: JohnnyTheTank

README.md

@@ -122,7 +122,6 @@ githubFactory.getEventsByUser({
 ## Github JSON API
 
 * docs: https://developer.github.com/v3/
-* api playground: https://apigee.com/console/github
 
 ## More angular-api-factories
 [bandsintown](https://github.com/JohnnyTheTank/angular-bandsintown-api-factory) - [dailymotion](https://github.com/JohnnyTheTank/angular-dailymotion-api-factory) - [facebook](https://github.com/JohnnyTheTank/angular-facebook-api-factory) - [footballdata](https://github.com/JohnnyTheTank/angular-footballdata-api-factory) - [flickr](https://github.com/JohnnyTheTank/angular-flickr-api-factory) - **github** - [openweathermap](https://github.com/JohnnyTheTank/angular-openweathermap-api-factory) - [tumblr](https://github.com/JohnnyTheTank/angular-tumblr-api-factory) - [vimeo](https://github.com/JohnnyTheTank/angular-vimeo-api-factory) - [wikipedia](https://github.com/JohnnyTheTank/angular-wikipedia-api-factory) - [youtube](https://github.com/JohnnyTheTank/angular-youtube-api-factory)