Implicitly adding padding between title-only groups can add extra noise

[epage]

From rust-lang/cargo#15942

[NOTE] waiting for foo v0.0.1 to be available at registry `alternative`
  |
[HELP] you may press ctrl-c to skip waiting; the crate should be available shortly

should probably be

[NOTE] waiting for foo v0.0.1 to be available at registry `alternative`
[HELP] you may press ctrl-c to skip waiting; the crate should be available shortly

[epage]

rustc requires this behavior. However, we could instead have rustc's emitter add a Padding.

Removing it would likely be a breaking change. However, we could possibly be smarter about when we insert it. Instead of it being based on group position, we can instead base it off of the title types for the groups. That is minor enough and maintains the intent of the rustc code so it likely wouldn't be a breaking change.