docs: Add instructions for disabling a workflow for a single subscriber [ticket DVRL-22]

[iampearceman]

[linear[bot]]

DVRL-22 add faq on how to disable a workflow only for one subscriber

### What? Subscribers can change their preference [https://docs.novu.co/subscribers/preferences](https://docs.novu.co/subscribers/preferences) ### Why? (Context) 1. Using subscriber preference feature subscribers can update preference for one workflow or if workflow is critical then subscribers can not manage preference 2. A workflow can be made active or not-active using workflow settings. But this will disable/enable for all subscribers 3. If subscriber disable all channels for workflow using subscriber preference then that workflow will be disabled for only that subscriber ### Definition of Done 1. Add this info with appropriate explanation in preference page FAQ