How to stop the OOB notification getting triggered upon rejection of service request?

Hi,

There is an OOB event named: workflow.notification which triggers a notification when the request is rejected. We have customized notifications for rejection and do not require the OOB one. 

I have checked from where this event is getting triggered and get to know that it is used in one of the "Workflow Activity Definition". As this is new for me so, before doing any changes, I want to know how I can stop this and what impact it can have on the instance.

Your help will be really appreciated.

Thanks and Regards

Suresh