Readme: remove dead dev dependency and maintenance badges (prebid#8849)

* Readme: remove dead dev dependency badge and issue

* Remove maintainability and add back issues

README.md

@@ -1,8 +1,6 @@
 [![Build Status](https://circleci.com/gh/prebid/Prebid.js.svg?style=svg)](https://circleci.com/gh/prebid/Prebid.js)
 [![Percentage of issues still open](http://isitmaintained.com/badge/open/prebid/Prebid.js.svg)](http://isitmaintained.com/project/prebid/Prebid.js "Percentage of issues still open")
-[![Code Climate](https://codeclimate.com/github/prebid/Prebid.js/badges/gpa.svg)](https://codeclimate.com/github/prebid/Prebid.js)
 [![Coverage Status](https://coveralls.io/repos/github/prebid/Prebid.js/badge.svg)](https://coveralls.io/github/prebid/Prebid.js)
-[![devDependencies Status](https://david-dm.org/prebid/Prebid.js/dev-status.svg)](https://david-dm.org/prebid/Prebid.js?type=dev)
 [![Total Alerts](https://img.shields.io/lgtm/alerts/g/prebid/Prebid.js.svg?logo=lgtm&logoWidth=18)](https://lgtm.com/projects/g/prebid/Prebid.js/alerts/)
 
 # Prebid.js