docs: remove output from command in Secure Gateways doc

[melsal13]

Description:

• remove output from 2 commands in Testing TLS Parameters section for v1.3
• remove output from 2 commands in Testing TLS Parameters section for latest
• specify in Testing TLS Parameters section that this test is for clusters without External LoadBalancer support

Page: https://gateway.envoyproxy.io/docs/tasks/security/secure-gateways/