Simplified "value must be defined" calls in fake automations repository (#28212)

towards https://linear.app/ghost/issue/NY-1286

This change should have no functionality impact.

Before this change, you supplied three fields to `requireValue`:

1. The row
2. The name of the field you want
3. The value of the field you want

Now, you only need to supply the first two. Also, you don't need to
supply a full row--just what's necessary.

I think this is a useful improvement on its own, but it also makes an
upcoming change a little simpler.