Hide feed, incoming email, and static access tokens by default

What does this MR do and why?

Describe in detail what your merge request does and why.

Enables the hide_access_tokens feature flag by default. This feature flag has already been enabled on gitlab.com.

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For context

Before	After

How to set up and validate locally

1. Open gitlab.yml in the gdk/gitlab directory. Find the incoming_email property and change enabled to true. Run gdk restart
2. Sign in as an Admin.
3. Navigate to /admin/application_settings/general. Open the Visibility and access controls section and ensure the Disable feed token checkbox is unchecked.
4. Navigate to /admin/application_settings/repository. Open the External storage for repository static objects section. Enter https://foo.bar for the External storage URL field and a random value (fdsafasdf) for External storage authentication token.
5. Navigate to /-/profile/personal_access_tokens

MR acceptance checklist

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