Update sip-telnyx.mdx

Author: sahilsuman933

fern/advanced/sip/sip-telnyx.mdx

@@ -50,7 +50,7 @@ To allow Vapi.ai to make outbound calls through your Telnyx account:
 1. **Set Up Outbound Authentication**
    - Go to Voice / SIP Trunking / Authentication and routing
    - Scroll down to "Outbound calls authentication"
-   - Select Tech Prefix and create a new credential for Vapi to use
+   - Create a new credential for Vapi to use
    <Frame>
      <img src="../../static/images/sip/telynx-outbound-auth.png" />
    </Frame>