Pin cython to unblock public CI (#2441)

This PR pins `cython <3.1` to w/a build failure observing with `3.1.0`
in public CI.
The latest stable Cython version was `3.0.12`.

Author: antonwolfy

conda-recipe/meta.yaml

@@ -13,7 +13,7 @@ requirements:
       - python
       - setuptools
       - numpy >=1.23
-      - cython
+      - cython <3.1
       - cmake >=3.21
       - ninja
       - git

environments/build_with_oneapi.yml

@@ -3,7 +3,7 @@ channels:
   - conda-forge
 dependencies:
   - cmake
-  - cython
+  - cython <3.1
   - ninja
   - numpy
   - pytest