Add more clarity about Kibana Custom Branding that requires an Enterprise subscription

[jeanfabrice]

Describe the feature:
In Kibana, the Advanced Setting section "Custom Branding" appears with any kind of license (Basic, Gold, Platinum, Enterprise, etc)

The "subscription required" link in the description text of the setting takes the user to a pretty generic landing page, which may create confusion.

As a user with a Free or Platinum subscription, I have access to these Kibana advanced settings:
I can upload a logo, see it rendered on the setting page, but I can't see it on Kibana Home page

The suggested feature is to completely hide the settings to the user when the current subscription is not compatible with Custom Branding / Custom Banner (as per https://www.elastic.co/subscriptions#service-54):

As a workaround, we can:

• improve the landing page (current: https://www.elastic.co/subscriptions) to redirect the user exactly to the Custom Branding / Custom Banner subsection
• If changing the link test is also an option, then using "Enterprise Subscription required" (for Custom branding) and "Platinum subscription required" (for Custom banner) in place of "Subscription required" would also help, as "Free" and "Gold" are also a valid subscriptions, that falls under the "Subscription required" terms

Describe a specific use case for the feature:
Not confuse the user with a feature that is not available for his subscription license

[elasticmachine]

Pinging @elastic/appex-sharedux (Team:SharedUX)

[sebelga]

We could work this issue along with #196659 as they are related in terms of showing/hidding sections based on the active user or space.