Remove unused code in app status test (#2020)
Remove unused code in app status test (#2020)

[changelog skip]

We needed `backlog` and `running` when we introduced the stats endpoint
in [c5aad50e][]. We changed the endpoint to use `@cli.stats` instead in
[c48b804d][], so these values are no longer needed.

[c5aad50e]: https://github.com/puma/puma/commit/c5aad50eb41ffc0540e655a0f016ee4fabdf1e97
[c48b804d]: https://github.com/puma/puma/commit/c48b804d8faf0b0d7910dde83a9cad2eb44a1ae4
looker/puma,puma/puma,puma/puma,puma/puma,eileencodes/puma,eileencodes/puma,looker/puma,eileencodes/puma,puma/puma,looker/puma,looker/puma,eileencodes/puma