Fix suggested alternative for deprecated Claude Sonnet 3.5

Current version is referencing itself.

I chose to recommend Claude Haiku 4.5 instead, as it was the replacement used in other parts of the documentation (see 1472523 )

Author: AlexanderMelde

data/tables/copilot/model-deprecation-history.yml

@@ -13,7 +13,7 @@
 
 - name: 'Claude Sonnet 3.5'
   retirement_date: '2025-11-06'
-  suggested_alternative: 'Claude Sonnet 3.5'
+  suggested_alternative: 'Claude Haiku 4.5'
 
 - name: 'Claude Opus 4'
   retirement_date: '2025-10-23'