Update customer_faq.md (#1155)
Update customer_faq.md (#1155)

* Update customer_faq.md

Quick hit edits to User FAQ
* Remove Docker EE references
* Added Community vs. Verified profile Question
* Q1 2018 product teaser removed.
* Buy / purchase references adjusted to "Subscription" / "subscribe"
* Removed "How can I become  a Publisher" because it was redundant with Publisher FAQ, Publisher onboarding, etc. other pages...
* Payment details -> I'm moving this entire section over to the "Upgrade your Plan" section. Pay via Docker deprecation means that content is _not purchased_ via Hub any longer. Additionally, for some time Docker Enterprise has _not been sold_ through Hub. Don't see any reason to keep this whole section here. _If anything, this would need to be a part of Digital / SaaS documentation._ I'm assuming that's tracked elsewhere and there's no dependency. Given all that, I think "Upgrade your Plan" is the only other sensible place for this content to live.. as it is the only other current place where payments are being made, and I don't see any similar references to billing in that section.

* Make headings consistent

docker/docker.github.io,docker/docker.github.io,docker/docker.github.io,thaJeztah/docker.github.io,thaJeztah/docker.github.io,thaJeztah/docker.github.io,thaJeztah/docker.github.io,thaJeztah/docker.github.io,docker/docker.github.io,docker/docker.github.io