This option is defined in the TeamRaiser event misc options. Follow the steps below to remove that.
  1. Select Fundraising > TeamRaiser
  2. Find and Edit the TeamRaiser
  3. Click 3. Select Event Options
  4. Under Related Actions, click Edit Advanced Options
  5. Click Define Misc Options
  6. Delete the value under "Event Shortcut URL DNS Display Name"
  7. Click Save