Remove the Wiki

After adding the FAQ.md to the repo, I realized that there was already one in the Wiki: https://gitlab.com/gitlab-org/gitlab-ui/wikis/Frequently-asked-questions

When I asked on Slack what we should to about this, @gtsiolis suggested the following:

Suggestion: To avoid this from happening again, I vote for removing wiki altogether. Wiki is already hidden for members and completely inaccessible for anonymous users because of the missing home page. See gitlab#22319 (closed), gitlab#22319 (closed), etc. Not sure if dogfooding two (one of them obsolete) wiki pages brings in much value.

To-do: Let’s merge FAQ contents and also go through the roadmap page where most of the items have been completed or replaced with newer initiatives. Maybe consider moving one or two items from the roadmap wiki to the WG epic in &950 if needed.

Todos

• Move questions from the wiki to FAQ.md
• Move items from the roadmap to the epic as needed
• Remove the Wiki