refactor: remove ps command

`ps` should be replaced by `enter` with a specified container id.

docs/appendices/0.20.0-migration-guide.md

@@ -13,6 +13,7 @@ The following commands were previously deprecated and were removed in this relea
 - `plugin`: Use `plugin:list` instead.
 - `proxy`: Use `proxy:report` instead.
 - `trace`: Use `trace:on` or `trace:off` instead.
+- `ps`: Use `enter` with a container ID instead to run `ps auxww` within a container.
 
 ## Deprecations
 

docs/deployment/process-management.md

@@ -3,7 +3,6 @@
 > New as of 0.3.14, Enhanced in 0.7.0
 
 ```
-ps <app>                                       # List processes running in app container(s)
 ps:inspect <app>                               # Displays a sanitized version of docker inspect for an app
 ps:rebuild <app>                               # Rebuild an app from source
 ps:rebuildall                                  # Rebuild all apps from source
@@ -25,14 +24,6 @@ By default, Dokku will only start a single `web` process - if defined - though p
 
 ## Usage
 
-### Listing processes running in an app container
-
-To find out if your application's containers are running the commands you expect, simply run the `ps` command against that application.
-
-```shell
-dokku ps node-js-app
-```
-
 ### Inspecting app containers
 
 > New as of 0.13.0