Revert "Bump minimum cython"

This reverts commit 40187b6.

Author: aaronreidsmith

build_tools/build_requirements.txt

@@ -1,7 +1,7 @@
 numpy>=2.0.0,<3
 scipy>=1.13.0,<2
 statsmodels>=0.14.5,<1
-cython>=3.1.0
+cython>=0.29,!=0.29.18,!=0.29.31
 scikit-learn>=0.22
 pandas>=0.19
 patsy

doc/whats_new.rst

@@ -16,7 +16,6 @@ v0.8.1) will document the latest features.
 * Add support for Numpy 2.x. See `#600 <https://github.com/alkaline-ml/pmdarima/pull/600>`_
 * Increase minimum required Scipy to ``1.13.0`` (See `#607 <https://github.com/alkaline-ml/pmdarima/pull/607>`_)
 * Increase minimum required statsmodels to ``1.14.5`` (See `#607 <https://github.com/alkaline-ml/pmdarima/pull/607>`_)
-* Building now requires Cython ``>=3.1.0`` (See `#607 <https://github.com/alkaline-ml/pmdarima/pull/607>`_)
 
 `v2.0.4 <https://alkaline-ml.com/pmdarima/2.0.4>`_
 --------------------------------------------------

pyproject.toml

@@ -3,7 +3,7 @@ requires = [
     "numpy==2.0.0",
     "scipy==1.13.0",
     "statsmodels==0.14.2",
-    "cython>=3.1.0",
+    "cython>=0.29,!=0.29.18,!=0.29.31",
     "setuptools>=42,!=50.0.0,<60.0; python_version < '3.10'",
     "setuptools>=42,!=50.0.0; python_version >= '3.10'",
 ]

requirements.txt

@@ -1,4 +1,5 @@
 joblib>=0.11
+Cython>=0.29,!=0.29.18,!=0.29.31
 numpy>=1.21.6
 pandas>=0.19
 scikit-learn>=0.22