Backport of 'Fix MCP tools checkbox visibility for Premium groups'

What does this MR do and why?

Backport of !238459 (merged) to the 18-10-stable-ee branch.

The "External MCP tools" checkbox in group Duo settings was gated by :ai_features (Ultimate-only), making it invisible to Premium groups. This contradicts the documentation which states MCP is available for Premium and above.

This fix replaces :ai_features with :ai_catalog, which is a Premium+ licensed feature and is consistent with how the rest of the AI Catalog MCP flow is gated.

• Original MR: !238459 (merged)

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• This MR is backporting a bug fix, documentation update, or spec fix, previously merged in the default branch.
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