Block on Autopilot in CI (#2941)

Autopilot has been doing well enough that I think it's worth blocking
on it now in CI so we get more obvious coverage (rather than me
polling).

Co-authored-by: Robert Bailey <robertbailey@google.com>

cloudbuild.yaml

@@ -323,7 +323,6 @@ steps:
     - 'us-west1'
     - "${_REGISTRY}"
   id: e2e-feature-gates-gke-autopilot
-  allowFailure: true # for now, run the step but don't block on it
   waitFor:
     - e2e-wait-to-become-leader
 
@@ -339,7 +338,6 @@ steps:
     - 'us-west1'
     - "${_REGISTRY}"
   id: e2e-stable-gke-autopilot
-  allowFailure: true # for now, run the step but don't block on it
   waitFor:
     - e2e-feature-gates-gke-autopilot