Please follow these instructions for removing a synced calendar from your Google Calendar (Classic Calendar):
- Open your Google Calendar in a web browser
- On the left side, under "My calendars" you will see the name of the calendar you synced
- If you hover your mouse over the calendar label an arrow will appear on the right side of the label
- Click the arrow and choose "Calendar settings" from the drop-down menu
- This will take you to a new page. Please make sure you are on the "Calendar Details" tab
- Scroll all the way to the bottom of the page and you will see "Delete calendar", please click the "Permanently delete this calendar" link
- Select the "Yes" checkbox, and then "Delete"