Reduce memory requirement on export_llama tests with no params

Pull Request resolved: #11175




@imported-using-ghimport

Differential Revision: [D75498713](https://our.internmc.facebook.com/intern/diff/D75498713/)
ghstack-source-id: 287631950

Author: jackzhxng

examples/models/llama/model_args.py

@@ -5,7 +5,7 @@
 @dataclass
 class ModelArgs:
     dim: int = 4096
-    n_layers: int = 8
+    n_layers: int = 1
     n_heads: int = 32
     n_kv_heads: Optional[int] = None
     vocab_size: int = 512  # Arbitrary value, should be defined later by tokenizer.