Unfortunately there’s no way to remove them from peoples’ My Tasks view.
The workaround most people use is to move them into the “Later” section, which can then be collapsed:
Project Template assigned tasks show up in My Tasks automatically - #5 by LenSantos
You can vote for a change in this functionality by upvoting this Product Feedback item:
Lastly, I would be remiss
if I didn’t mention that my Flowsana integration provides a solution for this as part of its Dynamic Duration-Based Workflow; basically, instead of assigning the tasks in the template, you put the name of each task’s assignee in an “Assigned To” custom field, and at the appropriate time (when the task’s dependencies are completed), Flowsana automatically assigns the task to the person in the Assign To field. You can read more about it here.