[Development] Deprecate usage of JIRA in MXNet

[szha]

Dear MXNet community,

In 2018, the community voted to use JIRA for tracking development. However, in the past two years people gradually favored using GitHub for tracking instead, and the JIRA conventions were not followed. In order to reduce confusion and centralize issue and task tracking, I propose that we stop using JIRA in favor of direct tracking in GitHub.

The arguments for introducing JIRA and what has changed since our last discussion are the following:

• JIRA makes it more discoverable on search engine.
  • what changed now is that GitHub issues are equally discoverable on search engines nowadays.
• JIRA makes it easier to manage larger projects
  • the unified tools in GitHub has become powerful enough to fulfill the same needs. the combination of issues, pull requests, milestones, and projects can it seamless for managing larger projects. we have had several large projects that used this approach and the tools prove to be sufficient.
• JIRA makes it easy for public access and issue management
  • nowadays, the development in mxnet's own CI labeling bot has helped make it possible for community members to directly classify issues and PRs with labels, which alleviated the need for needing another tool.

As such, I think the downside of using more than one tool now outweighs using GitHub features directly.

Let's discuss if there are any concerns on this. Otherwise I will open a vote in a week to finalize the decision. Thanks.

Best regards, Sheng

[szha]

Vote passed in https://lists.apache.org/thread.html/rc2b2615fd9b43d90f35b584621e1f57c08e221061ffdef60c15c14cb%40%3Cdev.mxnet.apache.org%3E Updating mentions of JIRA in #18992