Fix nightlies & untrack json files from git lfs (#414)

tests/data/lerobot/xarm_push_medium/train/dataset_info.json

@@ -1,3 +1,51 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:8133fe105b6e35182c4e24d8ac092730cb8f684f6591e4f1b3a4a2adaf224c46
-size 912
+{
+  "citation": "",
+  "description": "",
+  "features": {
+    "observation.image": {
+      "_type": "VideoFrame"
+    },
+    "observation.state": {
+      "feature": {
+        "dtype": "float32",
+        "_type": "Value"
+      },
+      "length": 4,
+      "_type": "Sequence"
+    },
+    "action": {
+      "feature": {
+        "dtype": "float32",
+        "_type": "Value"
+      },
+      "length": 3,
+      "_type": "Sequence"
+    },
+    "episode_index": {
+      "dtype": "int64",
+      "_type": "Value"
+    },
+    "frame_index": {
+      "dtype": "int64",
+      "_type": "Value"
+    },
+    "timestamp": {
+      "dtype": "float32",
+      "_type": "Value"
+    },
+    "next.reward": {
+      "dtype": "float32",
+      "_type": "Value"
+    },
+    "next.done": {
+      "dtype": "bool",
+      "_type": "Value"
+    },
+    "index": {
+      "dtype": "int64",
+      "_type": "Value"
+    }
+  },
+  "homepage": "",
+  "license": ""
+}

tests/data/lerobot/xarm_push_medium/train/state.json

@@ -1,3 +1,13 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:3ca324435b18abab8956aaac43bdac463e8881f654f7a851a39a7eb190e7e040
-size 247
+{
+  "_data_files": [
+    {
+      "filename": "data-00000-of-00001.arrow"
+    }
+  ],
+  "_fingerprint": "29f9b4c0ed32b18a",
+  "_format_columns": null,
+  "_format_kwargs": {},
+  "_format_type": null,
+  "_output_all_columns": false,
+  "_split": null
+}