HA runs in a different Docker container to core-ssh.
You’d need the other SSH add-on, that has the option to disable protection mode so that you can run docker commands.
Keep in mind that you risk breaking HA, and any changes you make will be lost when the HA container is rebuilt - such as when you restart the host, upgrade HA, and sometimes even just restart HA.
The correct solution is for the dev to fix the custom integration.
The proper way is to add the dependencies/requirements to the manifest.json of the integration, though. That way, HA will pull the packages automatically.
Using pip means you’ll have to redo it each time HA is upgraded.