Remove experiment settings check for chat

What does this MR do and why?

This MR makes it so that experimental features do not need to be enabled to use Duo Chat.

A feature flag duo_chat_ga has been added. This will switch the :chat feature from being in BETA to be in GA.

Once :chat is in GA, it will show up regardless of the status of namespace experimental features toggle.

If :chat is still in Beta, it will only show up when namespace experimental features toggle is on.

Closes https://gitlab.com/gitlab-org/gitlab/-/issues/455506

Closes https://gitlab.com/gitlab-org/gitlab/-/issues/442186

MR acceptance checklist

✅

Screenshots or screen recordings

• SaaS Part 1, Part 2
• SM

Here are the settings

How to set up and validate locally

1. Go to the admin area of an Ultimate/Premium group. With the free tier, Duo Chat should not appear.
2. If 'Use Duo features' is checked, Duo Chat should show up on the upper right when on the group page

• It should show up even when 'Use experiment and beta features' is unchecked.

3. If 'Use Duo features' is unchecked, Duo Chat should not show up on the upper right when on the group page