Clean up dependencies

Author: blink1073

setup.cfg

@@ -16,7 +16,6 @@ classifiers =
     Intended Audience :: Science/Research
     License :: OSI Approved :: BSD License
     Programming Language :: Python
-    Programming Language :: Python :: 3.6
     Programming Language :: Python :: 3.7
     Programming Language :: Python :: 3.8
     Programming Language :: Python :: 3.9
@@ -26,11 +25,11 @@ classifiers =
 zip_safe = False
 include_package_data = True
 packages = find:
-python_requires = >=3.6
+python_requires = >=3.7
 install_requires =
-    jupyter_server>=1,<2
+    jupyter_server>=1
     terminado>=0.8.3
-    pywinpty(<2);os_name=='nt'
+    pywinpty;os_name=='nt'
 
 [options.extras_require]
 test =