Revert yieldy behavior for non-use Suspense (#25537)

To derisk the rollout of `use`, and simplify the implementation, this
reverts the yield-to-microtasks behavior for promises that are thrown
directly (as opposed to being unwrapped by `use`).

We may add this back later. However, the plan is to deprecate throwing a
promise directly and migrate all existing Suspense code to `use`, so the
extra code probably isn't worth it.