improve(flan-t5): update default generation config

Signed-off-by: Aaron <29749331+aarnphm@users.noreply.github.com>

src/openllm/models/flan_t5/configuration_flan_t5.py

@@ -50,8 +50,8 @@ class FlanT5Config(openllm.LLMConfig):
     """Configuration for the FLAN-T5 model."""
 
     class GenerationConfig:
-        temperature: float = 0.75
-        max_length: int = 3000
+        temperature: float = 0.3
+        max_length: int = 400
         top_k: int = 50
         top_p: float = 0.4
         repetition_penalty = 1.0