add `mobilebert` onnx configs (#17029)
* update docs of length_penalty
* Revert "update docs of length_penalty"
This reverts commit 466bf4800b75ec29bd2ff75bad8e8973bd98d01c.
* add mobilebert onnx config
* address suggestions
* Update auto.mdx
* Update __init__.py
* Update features.py
