Remove -i options from mv, rm and cp aliases

This was arguably useful in the terminal, but it means these aliases
can't be used from any of the ZMQ frontends. And users familiar with the
shell shouldn't find the default (non -i) behaviour surprising.

Closes gh-5729, which accidentally included an unrelated change.

IPython/core/alias.py

@@ -50,7 +50,7 b' def default_aliases():'
 
     if os.name == 'posix':
         default_aliases = [('mkdir', 'mkdir'), ('rmdir', 'rmdir'),
-                           ('mv', 'mv -i'), ('rm', 'rm -i'), ('cp', 'cp -i'),
+                           ('mv', 'mv'), ('rm', 'rm'), ('cp', 'cp'),
                            ('cat', 'cat'),
                            ]
         # Useful set of ls aliases.  The GNU and BSD options are a little