docs: updates task testing instructions to use tabs for with|without …

[eitansuez]

…external load balancer (fixes #3259)

What type of PR is this?

Updates tasks in docs to use tabs for testing with & without load balancer support:

• tasks/traffic/http3.md
• tasks/security/tls-passthrough.md
• tasks/security/secure-gateways.md
• tasks/security/backend-tls.md
• tasks/security/mutual-tls.md
• tasks/security/tls-termination.md

Also reverses the order: with lb support first, without second.

Fixes #3259