rpcuser.py: Use 'python' not 'python2'

share/rpcuser/rpcuser.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python2 
+#!/usr/bin/env python
 # Copyright (c) 2015-2016 The Bitcoin Core developers
 # Distributed under the MIT software license, see the accompanying 
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.