Do not auto-retry native builds before tests

[ofalvai]

Context

E2E tests perform full native xcodebuild/gradle builds, and those builds can fail for various reasons (this is a kind of verification, even before any E2E test case actually runs). At the moment, those failures are retried automatically, citing:

The first time an iOS project is built, it fails because it does not finish building libReact.a before it builds the test app.

This is probably no longer true, and the retry makes test runs unnecessarily long when there is a genuine failure.

Changes

Remove that retry logic completely.

Also, the old iOS handler ended in return null on the second failure, so a genuinely broken build resolved as success and the failure surfaced later as a confusing "app not installed" error. Now a bad xcodebuild rejects and fails the run directly.

Edit: re-ran CI 4 times just to see if it's flaky, but every run was green.