Rephrase enableAskAiSuggestion description to drop native-impl detail

Addresses Cursor Bugbot finding: the "back-compat with older native
clients" phrasing in the schema description leaked native-side detail
into the generated TS type comment. Replaced with the more neutral
"for backward compatibility", matching the framing used by other
OmnibarConfig fields like enableVoiceChatAccess.

No behaviour change.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: tomasstrba

special-pages/pages/new-tab/messages/types/omnibar-config.json

@@ -133,7 +133,7 @@
     },
     "enableAskAiSuggestion": {
       "title": "Enable Ask Duck.ai Suggestion",
-      "description": "Controls whether the inline 'Ask Duck.ai: <query>' suggestion is rendered in the omnibar dropdown. Missing/undefined is treated as true for back-compat with older native clients. Does not affect the Duck.ai mode pill or any other AI affordance — those remain governed by enableAi.",
+      "description": "Controls whether the inline 'Ask Duck.ai: <query>' suggestion is rendered in the omnibar dropdown. Missing/undefined is treated as true for backward compatibility. Does not affect the Duck.ai mode pill or any other AI affordance — those remain governed by enableAi.",
       "type": "boolean",
       "default": true
     }

special-pages/pages/new-tab/types/new-tab.ts

@@ -111,7 +111,7 @@ export type EnableWebSearch = boolean;
  */
 export type EnableVoiceChatAccess = boolean;
 /**
- * Controls whether the inline 'Ask Duck.ai: <query>' suggestion is rendered in the omnibar dropdown. Missing/undefined is treated as true for back-compat with older native clients. Does not affect the Duck.ai mode pill or any other AI affordance — those remain governed by enableAi.
+ * Controls whether the inline 'Ask Duck.ai: <query>' suggestion is rendered in the omnibar dropdown. Missing/undefined is treated as true for backward compatibility. Does not affect the Duck.ai mode pill or any other AI affordance — those remain governed by enableAi.
  */
 export type EnableAskDuckAiSuggestion = boolean;
 export type FeedType = "privacy-stats" | "activity";