[enh] dh_python2 replaces shebang during build. Using the correct one in source directly

bin/yunohost

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#! /usr/bin/python
 # -*- coding: utf-8 -*-
 
 import sys

bin/yunohost-api

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#! /usr/bin/python
 # -*- coding: utf-8 -*-
 
 import sys