Add license check to authorizer

What does this MR do and why?

Previously in the Authorizer class there were no license check, leading to groups with experiment and beta feature enabled to have access to chat even without Ultimate license. This is a fix.

Screenshots or screen recordings

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Before	After

How to set up and validate locally

1. In rails console change settings of a group without plan

   Group.last.namespace_settings.update_column(:experiment_features_enabled, true)

2. Try asking about an issue in this group - you should see the answer.
3. Switch to this branch
4. Try asking about an issue in this group - you should see the information about the wrong pricing tier.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

solves #431209 (closed)