removing the sidecars by default

General MR

Summary

As we want to keep supporting 1.27.x, we need to turn off istio sidecars by default.

Relevant logs/screenshots

n/a

Linked Issue

• gitlab#215 (closed)
• gitlab-runner#69 (closed)

Upgrade Notices

This removes the upgrade notice for Istio 1.20.4-bb.2 as sidecars will not be turned on by default.