Update config.json

Rename key "pretrained_path" to "checkpoint_path" due to this issue
"""
raise DecodingError(path, f"The fields {formatted_keys} are not valid for {stringify_type(cls)}")
draccus.utils.DecodingError: The fields `pretrained_path` are not valid for ACTConfig
"""

config.json

@@ -40,7 +40,7 @@
     "private": null,
     "tags": null,
     "license": null,
-    "pretrained_path": null,
+    "checkpoint_path": null,
     "chunk_size": 100,
     "n_action_steps": 100,
     "normalization_mapping": {