You can remove the add-in from inside ArcGIS Pro.
In ArcGIS Pro, click Project, then Add-In Manager.
Select the TravelTime add-in.
Click Delete this Add-In.
Restart ArcGIS Pro.
To install the add-in again, see How do I install the ArcGIS Pro add-in?
How to uninstall the TravelTime add-in for ArcGIS Pro.