First, start deleting the integration in Pipedrive. For that, go to Toky landing page in Pipedrive marketplace here
Then click on Manage, that will take you to the Pipedrive page to uninstall the Toky application.
Click on the trash icon and confirm. Now the app should be uninstalled in Pipedrive.
After deleting the integration in Pipedrive, in Toky integration page look for "Delete Integration" and confirm.
After following those steps, the integration should be unistalled.