docs: drop advanced usage

Dokku internals shouldn't be exposed in docs. Additionally, the internals here are likely to change in the future as this moves to the upcoming prop binary, so having incorrect docs will hinder that move.

docs/advanced-usage/docker-options.md

@@ -119,25 +119,3 @@ You can pass flags which will output only the value of the specific information
 ```shell
 dokku docker-options:report node-js-app --docker-options-build
 ```
-
-## Advanced usage
-
-In your applications folder `/home/dokku/app_name` create a file called `DOCKER_OPTIONS_RUN` (or `DOCKER_OPTIONS_BUILD` or `DOCKER_OPTIONS_DEPLOY`).
-
-Inside this file list one Docker option per line. For example:
-
-```shell
---link container_name:alias
--v /host/path:/container/path
--v /another/container/path
-```
-
-The above example will result in the following options being passed to Docker during `dokku run`:
-
-```shell
---link container_name:alias -v /host/path:/container/path -v /another/container/path
-```
-
-You may also include comments (lines beginning with a #) and blank lines in the DOCKER_OPTIONS file.
-
-More information on Docker options can be found here: https://docs.docker.com/engine/reference/commandline/run/.