Fix shebang for modules.env sort check script

It is obviously missing "python" which makes it not possible to run on
its own. It works with tox because tox.ini explicitly invokes it with
"python {toxinidir}/tools/sorted_modules_env.py".

Change-Id: I6eab942660d69eacda95572c7d2077687087b7c7

tools/sorted_modules_env.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env
+#!/usr/bin/env python
 
 import sys
 import difflib