Update how-to-create-test-certificates.md

Change from **self** to **CA** in **CA-signed certificates** section.

Author: lakbychance

articles/iot-edge/how-to-create-test-certificates.md

@@ -357,7 +357,7 @@ Your IoT device also needs a copy of its device certificates so that it can auth
 
 ### CA-signed certificates
 
-When you authenticate an IoT device with self-signed certificates, you need to upload the root CA certificate for your solution to IoT Hub.
+When you authenticate an IoT device with CA-signed certificates, you need to upload the root CA certificate for your solution to IoT Hub.
 Then, you perform a verification to prove to IoT Hub that you own the root CA certificate.
 Finally, you use the same root CA certificate to create device certificates to put on your IoT device so that it can authenticate with IoT Hub.