Hello, @techwithanirudh! 
We recently revamped our problem check system to support more use cases, and we currently do not have a mechanism to clear notices from plugins when they are uninstalled. It’s something we’re working on.
For now, you can try the following console commands to clear the notices:
ProblemCheckTracker.where(identifier: "discourse_automation").delete_all
AdminNotice.where(identifier: "discourse_automation").delete_all