Remove broken screenshot

This was removed when changing to the new layout.
See 0c6eacf

Removing screenshot in README instead of updating, as it's easier to
keep up to date.

Author: kitop

README.md

@@ -16,8 +16,6 @@ The spec is published and versioned for various ecosystems:
 
 You can view the definition using [Swagger UI](https://swagger.io/tools/swagger-ui/) by visiting [open-api.netlify.com](http://open-api.netlify.com) which provides limited interaction with the API from the browser.
 
-[![screenshot of netlify swagger ui](ui/screenshot.png)](https://open-api.netlify.com)
-
 ### Go Client
 
 [![GoDoc][godoc-img]][godoc]