Update docker.md

[nbelakovski-mssm]

The second line calling deid locally after running the docker container doesn't make any sense. Also I think that adding --help helps to show how this docker container could be used.

Description

Related issues: N/A

Checklist

• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• My code follows the style guidelines of this project

Open questions

Questions that require more discussion or to be addressed in future development: N/A

[vsoch]

@nbelakovski-mssm the CI failure is not your fault - we just need to update the formatter. I'll fix this and give you something to rebase against.