Revert "Revert "ci: revert EngFlow ios_build changes (#1700)" (#1704)" (#1711)
Revert "Revert "ci: revert EngFlow ios_build changes (#1700)" (#1704)" (#1711)

Description: This reverts commit 35ac59d54f4172e60c6bc902776c2254b43bc880.

The RBE ios_build job has been timing out every time in CI, and switching back to running on GHA runners resolves the issue.

Signed-off-by: Mike Schore <270e364e708f2af319f244c09ceba52a03dbd980@gmail.com>
envoyproxy/envoy-mobile,envoyproxy/envoy-mobile,envoyproxy/envoy-mobile,envoyproxy/envoy-mobile,envoyproxy/envoy-mobile,envoyproxy/envoy-mobile,envoyproxy/envoy-mobile,envoyproxy/envoy-mobile,envoyproxy/envoy-mobile