README: Remove IRC references and update bug reporting link (#4879)

* [UPDATE] IRC on Readme.

* Removed IRC references

* let's fix bug reporting link as well

Author: apurv-1

README.md

@@ -81,11 +81,7 @@ Mailing lists:
 - [Issues Mailing List](mailto:issues-subscribe@cloudstack.apache.org)
 - [Marketing Mailing List](mailto:marketing-subscribe@cloudstack.apache.org)
 
-IRC, join us on irc.freenode.net on:
-- `#cloudstack`: General Apache CloudStack conversation and end user support
-- `#cloudstack-dev`: Development discussions
-
-Report and/or check bugs on [JIRA](https://issues.apache.org/jira/browse/CLOUDSTACK) and check our
+Report and/or check bugs on [Github](https://github.com/apache/cloudstack/issues) and check our
 developer [page](http://cloudstack.apache.org/developers.html) for contributing code.
 
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