[MAINT] Pinning Cython to <3.1 temporarily (#5056)

- pin cython to <3.1

Author: IAlibay

.github/workflows/gh-ci.yaml

@@ -92,6 +92,8 @@ jobs:
         full-deps: ${{ matrix.full-deps }}
         # disable GSD because it occasionally introduce hanging in testing #4209
         gsd: ''
+        # pin cython
+        cython: 'cython<3.1'
         # in most cases will just default to empty, i.e. pick up max version from other deps
         numpy: ${{ matrix.numpy }}
         extra-pip-deps: ${{ matrix.extra-pip-deps }}

package/pyproject.toml

@@ -1,7 +1,7 @@
 [build-system]
 # Minimum requirements for the build system to execute
 requires = [
-    "Cython>=0.28",
+    "Cython>=0.28,<3.1",
     "packaging",
     # numpy requirement for wheel builds for distribution on PyPI - building
     # against 2.x yields wheels that are also compatible with numpy 1.x at