Revert #99 (#104)

Author: eriknw

pyproject.toml

@@ -4,7 +4,7 @@ requires = [
     "setuptools >=64",
     "setuptools-git-versioning",
     "wheel",
-    "cffi>=1.11,<1.16",
+    "cffi>=1.11",
     "cython",
     "oldest-supported-numpy; platform_python_implementation != 'PyPy'",
     # Inspired by SciPy: unpin numpy version for PyPy builds,