Fixes https://github.com/microsoft/rhobotics/issues/53 for this checkpoint.
Removes `data_config.json` and `stats.json`, which were made for a TabletopSim dataset, and drops them from `manifest.json`. Pretraining normalized each robot's data with its own statistics, so no single set of statistics fits this checkpoint.
Fine-tuning is unaffected. Evaluating or serving `rho-base` directly now needs a dataset configuration for the target robot; https://github.com/microsoft/rhobotics/pull/77 makes loading without one fail with a clear message.
