remove redundant cls alias on Windows

It's already a magic, and the duplicate alias was failing with Invalid alias.

IPython/terminal/interactiveshell.py

@@ -379,9 +379,6 b' class TerminalInteractiveShell(InteractiveShell):'
         if os.name == 'posix':
             aliases = [('clear', 'clear'), ('more', 'more'), ('less', 'less'),
                        ('man', 'man')]
-        elif os.name == 'nt':
-            aliases = [('cls', 'cls')]
-
 
         for name, cmd in aliases:
             self.alias_manager.soft_define_alias(name, cmd)