Daigo 3 Dango authored Jan 27, 2020 and Nathan Ladd committed Feb 19, 2020

Pin rack version to 2.0.8. Rack-2.1.0 and 2.1.1 are known to record error below upon requests to `/sidekiq`:

```
NoMethodError - undefined method `transform_keys' for #<ActionDispatch::Request::Session:0x...>
```