Remove jax.interpreters.xla.lower_fun.

This function has been a stub that does nothing useful for a long time, and the only user I can find is Equinox which already guards this with a hasattr(xla, 'lower_fun') guard.

PiperOrigin-RevId: 510142446

jax/_src/interpreters/xla.py

@@ -568,13 +568,3 @@ def __missing__(self, key):
 
 backend_specific_translations: Dict[str, _TranslationRuleAdapter]
 backend_specific_translations = _BackendSpecificTranslationsAdapter()
-
-# TODO(phawkins): remove lower_fun completely after updating users.
-def lower_fun(fun: Callable, *, multiple_results: bool, backend=None,
-              new_style: bool = False) -> Callable:
-  def f(*args, **kw):
-    raise RuntimeError("XLA translation rules are deprecated and "
-                       "jax.interpreters.xla.lower_fun is no longer supported. "
-                       "Add an MLIR lowering via jax.interpreters.mlir "
-                       "instead.")
-  return f

jax/interpreters/xla.py

@@ -40,7 +40,6 @@
   extend_axis_env as extend_axis_env,
   extend_name_stack as extend_name_stack,
   jaxpr_collectives as jaxpr_collectives,
-  lower_fun as lower_fun,
   make_device_array as make_device_array,
   make_op_metadata as make_op_metadata,
   new_name_stack as new_name_stack,