Removing this tested but otherwise unused method makes it easier to merge https://github.com/tensorflow/tensorflow/pull/56202 which changes the API contract of (undocumented) method .walk().
Technically speaking changing the contract of .walk() breaks backward compatibility, but we've never advertised its existence and as far as I can tell it has no users in the code I have access to.
PiperOrigin-RevId: 455687311
Changed the behavior of `jacfwd`, `jacrev`, and `grad` when the input
pytree elements have heterogeneous dtypes, e.g., real and complex
elements:
* Changed the dtypes of the pytree elements of the Jacobian produced by
jacfwd to be those of the input tangent basis.
* Changed the dtypes of the pytree elements of the Jacobian produced by
jacrev to be those of the output tangent basis.
* Changed the dtypes of the pytree elements of the primals and tangents
produced by jacfwd and jacrev to be the same as the corresponding
elements in the input.
Changed the behavior of the flags to `jacfwd` and `jacrev`:
* Changed the allow_int flag to only allows integer and Boolean dtypes.
Previously, this flag allowed all other types.
Note that a few call sites in the diff got a ``# type: ignore``, because
the latest jaxlib does not have up-to-date signatures for the correpsonding
callables.
