Fix command quotes

Author: PatAltimore

articles/iot-edge/how-to-provision-single-device-linux-symmetric.md

@@ -76,7 +76,7 @@ Now that the container engine and the IoT Edge runtime are installed on your dev
 You can quickly configure your IoT Edge device with symmetric key authentication using the following command:
 
    ```bash
-   sudo iotedge config mp --connection-string `PASTE_DEVICE_CONNECTION_STRING_HERE`
+   sudo iotedge config mp --connection-string 'PASTE_DEVICE_CONNECTION_STRING_HERE'
    ```
 
    This `iotedge config mp` command creates a configuration file on the device and enters your connection string in the configuration file.