fix: replace deprecated rerank v2 with rerank v3.5 (cohere-ai#710)

Author: walterbm-cohere

tests/test_async_client.py

@@ -169,7 +169,7 @@ async def test_rerank(self) -> None:
             'Capital punishment (the death penalty) has existed in the United States since beforethe United States was a country. As of 2017, capital punishment is legal in 30 of the 50 states.']
 
         response = await self.co.rerank(
-            model='rerank-english-v2.0',
+            model='rerank-v3.5',
             query='What is the capital of the United States?',
             documents=docs,
             top_n=3,

tests/test_client.py

@@ -206,7 +206,7 @@ def test_rerank(self) -> None:
             'Capital punishment (the death penalty) has existed in the United States since beforethe United States was a country. As of 2017, capital punishment is legal in 30 of the 50 states.']
 
         response = co.rerank(
-            model='rerank-english-v2.0',
+            model='rerank-v3.5',
             query='What is the capital of the United States?',
             documents=docs,
             top_n=3,