Turning duckAiUsageWarnings ON to internal users (#9921)

Task/Issue URL:
https://app.asana.com/1/137249556945/project/72649045549333/task/1219075630109594?focus=true
Tech Design URL (if applicable): 
API Proposals URL(s) (if applicable):

### Description
Turn the duckAiUsageWarnings on for all internal users, ahead of
external release next week.


### Steps to test this PR
- [ ] Fresh internal install. 
- [ ] Open Feature Flags settings and make sure `duckAiUsageWarnings` is
ON by default

### UI changes
No UI Changes

Author: YoussefKeyrouz

duckchat/duckchat-impl/src/main/java/com/duckduckgo/duckchat/impl/feature/DuckChatFeature.kt

@@ -325,8 +325,8 @@ interface DuckChatFeature {
 
     /**
      * @return `true` when native Duck.ai usage-limit and high-usage model notices may be shown.
-     * If the remote feature is not present defaults to `false`.
+     * If the remote feature is not present defaults to `internal`.
      */
-    @Toggle.DefaultValue(DefaultFeatureValue.FALSE)
+    @Toggle.DefaultValue(DefaultFeatureValue.INTERNAL)
     fun duckAiUsageWarnings(): Toggle
 }