Add a note to not follow remote access post-instructions for linux

[mradcliffe]

• 1. The Post-installation instructions on Docker are confusing as "Troubleshooting" isn't necessarily understandable.
• 2. The Post-installation instructions on DDev are confusing for the same reason.

Basically answer the question "Where do we stop" and when to return to the Quicksprint instructions.

[rfay]

Probably both ddev and quicksprint instructions should just say "Add your user to the docker group with
(sudo groupadd docker || true) && sudo usermod -aG docker $USER`