Update python version sanity check

setup.py

@@ -19,16 +19,10 @@
 name = "jupyter_server"
 
 # Minimal Python version sanity check
-if sys.platform == 'win32':
-    if sys.version_info < (3,7):
-        error = "ERROR: %s requires Python version 3.7 or above." % name
-        print(error, file=sys.stderr)
-        sys.exit(1)
-else:
-    if sys.version_info < (3,5):
-        error = "ERROR: %s requires Python version 3.5 or above." % name
-        print(error, file=sys.stderr)
-        sys.exit(1)
+if sys.version_info < (3,5):
+    error = "ERROR: %s requires Python version 3.5 or above." % name
+    print(error, file=sys.stderr)
+    sys.exit(1)
 
 # At least we're on the python version we need, move on.