convert logger.error to logger.warning (#636)

vocode/streaming/telephony/client/twilio_client.py

@@ -63,7 +63,7 @@ async def create_call(
         ) as response:
             if not response.ok:
                 if response.status == 400:
-                    logger.error(
+                    logger.warning(
                         f"Failed to create call: {response.status} {response.reason} {await response.json()}"
                     )
                     raise TwilioBadRequestException(