fix: parse moe_layer_freq from string to list in Megatron config adapter

Author: Xiaoming-AMD

tests/trainer/test_megatron_trainer.py

@@ -145,16 +145,12 @@ def test_deepseek_v2_lite(self):
             exp_path="examples/megatron/configs/MI300X/deepseek_v2_lite-pretrain.yaml",
             env_override={},
             extra_args=[
-                "--num_layers",
-                "4",
                 "--train_iters",
                 "3",
                 "--micro_batch_size",
                 "1",
                 "--global_batch_size",
                 "8",
-                "--moe_layer_freq",
-                "[0]*1+[1]*3",
                 "--expert_model_parallel_size",
                 "8",
             ],