(docs) update migration guide

docs/my-website/docs/migration.md

@@ -1,4 +1,4 @@
-# Migration
+# Migration Guide - LiteLLM v1.0.0+ 
 
 When we have breaking changes (i.e. going from 1.x.x to 2.x.x), we will document those changes here.
 
@@ -16,6 +16,11 @@ When we have breaking changes (i.e. going from 1.x.x to 2.x.x), we will document
     - `litellm.Litellm(api_key="sk-123")`
 - response objects now inherit from `BaseModel` (prev. `OpenAIObject`)
 - *NEW* default exception - `APIConnectionError` (prev. `APIError`)
+- litellm.get_max_tokens() now returns an int not a dict
+    ```python
+    max_tokens = litellm.get_max_tokens("gpt-3.5-turbo") # returns an int not a dict 
+    assert max_tokens==4097
+    ```
 
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