Fix HUB-02: correct declared weights filename

zm_config.json

@@ -4,7 +4,7 @@
   "model_module": "zeromodels.models.gpt2",
   "model_class": "GPT2Model",
   "variant": "gpt2_large",
-  "weights": "model.weights.json",
+  "weights": "model.weights.h5",
   "schema_version": 2,
   "weight_dtype": "float32",
   "model_type": "gpt2",
@@ -18,4 +18,4 @@
     "norm_eps": 1e-05,
     "tie_embeddings": true
   }
-}
+}