Release 0.19.4

# History

## 0.19.4

Install/update via the bootstrap script:

```shell
wget https://raw.githubusercontent.com/dokku/dokku/v0.19.4/bootstrap.sh
sudo DOKKU_TAG=v0.19.4 bash bootstrap.sh
```

### Bug Fixes

- #3755: @dean1012 Warn if key_file is missing on install but do not exit

debian/control

@@ -1,5 +1,5 @@
 Package: dokku
-Version: 0.19.3
+Version: 0.19.4
 Section: web
 Priority: optional
 Architecture: amd64