Stop shadowing free function (#6076)

I think this is currently working because [the function defined in fil.h is templated](https://github.com/rapidsai/cuml/blob/branch-24.10/python/cuml/cuml/fil/fil.pyx#L324), whereas the base C free function is not, and so Cython is parsing this correctly. However, not all versions of Cython can parse this correctly, and cuml currently fails to build on the trunk of Cython repository as a result.

Authors:
  - Vyas Ramasubramani (https://github.com/vyasr)

Approvers:
  - Dante Gama Dessavre (https://github.com/dantegd)
  - Bradley Dice (https://github.com/bdice)

URL: #6076

python/cuml/cuml/fil/fil.pyx

@@ -26,7 +26,7 @@ rmm = gpu_only_import('rmm')
 
 from libcpp cimport bool
 from libc.stdint cimport uintptr_t
-from libc.stdlib cimport free
+from libc.stdlib cimport free as c_free
 
 import cuml.internals
 from cuml.internals.array import CumlArray
@@ -545,7 +545,7 @@ cdef class ForestInference_impl():
         treelite_params.threads_per_tree = kwargs['threads_per_tree']
         if kwargs['compute_shape_str']:
             if self.shape_str:
-                free(self.shape_str)
+                c_free(self.shape_str)
             treelite_params.pforest_shape_str = &self.shape_str
         else:
             treelite_params.pforest_shape_str = NULL