Less strict scipy pinning because it is not available in Python 3.7

Author: basnijholt

setup.py

@@ -25,7 +25,7 @@ def get_version_and_cmdclass(package_name):
 
 
 install_requires = [
-    "scipy >= 1.8",
+    "scipy",
     "sortedcollections >= 1.1",
     "sortedcontainers >= 2.0",
     "cloudpickle",