Hide scheduled at row for unscheduled objects

[pezholio]

At the moment, we show “Scheduled at” for any blocks that have ever been scheduled, even if they have since been published. Additionally, we show a blank line for blocks that have never been scheduled.

This hides the "Scheduled at" row unless something is currently awaiting publication.

I've also titleized the block's status, which looks a bit nicer

Screenshots

Before

After

[pezholio]

@tahb Yeah, I thought we were keeping the views as unintelligent for that PR then coming back to them. I like copying the approach from Whitehall, but I feel like this is a smaller step, and gets rid of potentially misleading / confusing info