Changed system prompt to user

src/deepeval/base_task.py

@@ -142,11 +142,11 @@ class BaseTask(ABC):
             self.model.config.pad_token_id = self.tokenizer.eos_token_id
 
         chat = [
-            {"role": "system", "content": "You are a helpful AI assistant."},
+            {"role": "user", "content": "You are a helpful AI assistant."},
             {"role": "assistant", "content": "I am here to help you with any questions you may have."},
             {"role": "user", "content": prompt},
         ]
-
+        
         formatted_chat = self.tokenizer.apply_chat_template(
             chat,
             tokenize=False,