How to remove an existing connection in Excel file.

Hello,

When clicking on Data tab  in an Excel file, choosing Existing Connections, a small box Existing connections is displayed. As usual, when I click on one of connections in the part Connections in this workbook of Existing Connections box,  Import Data box is displayed, then I choose Properties, Connection Properties box will be displayed. However, when clicking on the Test connection in the part Connections in this Workbook (like the picture below) , an Import Data box is displayed, then I click on Properties in this box, this Import Data box is still displayed again, not a connection Properties box.

I want to remove an existing connection in an excel file. How can I remove this Test connection? 

Existing Connections

Thank you,