Replace mjs_detachBody and mjs_detachDefault with mjs_detach.

In a follow-up, mjs_detach will be changed to only remove without deleting an element.

PiperOrigin-RevId: 773637351
Change-Id: I9ee4d3584ba88ccc225591337cf036bab806e25c

python/mjspec.ipynb

@@ -2000,7 +2000,7 @@
     "\n",
     "# Delete all key frames to avoid name conflicts\n",
     "while humanoid.keys:\n",
-    "  humanoid.keys[-1].delete()\n",
+    "  humanoid.delete(keys[-1])\n",
     "\n",
     "# Create a grid of humanoids by attaching humanoid to spec multiple times\n",
     "for i in range(4):\n",
@@ -2335,7 +2335,7 @@
     "fly = mj.MjSpec.from_file(fly_file)\n",
     "# Remove lights from fly so they are not duplicated in line-up\n",
     "for light in fly.lights:\n",
-    "  light.delete()\n",
+    "  fly.delete(light)\n",
     "\n",
     "small_fly = scale_spec(fly, 1.25)\n",
     "large_fly = scale_spec(fly, 2)\n",