You will need the Connections Settings permission to perform this action.
Click on "Connections" from the left hand navigation. Afterwards, click on the arrow next to the "Add New" button and select "Settings."
A pop up will appear. Choose the connection type you want to remove from the drop down and then click on the red "Delete Type" button. A confirmation message will appear. Click on "Yes" to finish deleting the type.
Helpful Tips
Instead of deleting a connection type, you can instead deactivate it so that new connections cannot use that type. This is recommended to keep historical data. After selecting the type from the drop down, change the "Active?" field to "No" and then hit the "Save" button.