Revert "push version requirements"

This reverts commit dce4a11.

Author: Jonathan Kliem

.github/workflows/build_wheels.yml

@@ -18,7 +18,7 @@ jobs:
       - uses: actions/checkout@v2
 
       - name: Build wheels
-        uses: pypa/cibuildwheel@v2.3.1
+        uses: pypa/cibuildwheel@v2.1.3
         # to supply options, put them in 'env', like:
         # env:
         #     CIBW_SOME_OPTION: value

pyproject.toml

@@ -1,3 +1,3 @@
 [build-system]
-requires = ["setuptools", "wheel", "Cython>=0.29.28"]
+requires = ["setuptools", "wheel", "Cython"]
 build-backend = "setuptools.build_meta"