'IF' statement is deprecated and will be removed in a future Cython version. #25652
Description
When building with Cython 3.0, the following warning appears multiple times:
warning: sklearn/cluster/_k_means_elkan.pyx:9:0: The 'IF' statement is deprecated and will be removed in a future Cython version. Consider using runtime conditions or C macros instead. See cython/cython#4310
This is related to how we use SKLEARN_OPENMP_PARALLELISM_ENABLED during compile-time. XREF: cython/cython#4310