toolbox/generate-input.h-labels.py: python3.

Test: treehugger
Change-Id: Ia63fd0db0b678de05ab2a83411f7a04d81e401e9
diff --git a/toolbox/generate-input.h-labels.py b/toolbox/generate-input.h-labels.py
index c0e9fce..20db638 100755
--- a/toolbox/generate-input.h-labels.py
+++ b/toolbox/generate-input.h-labels.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 # Copyright (C) 2015 The Android Open Source Project
 #
@@ -16,7 +16,7 @@
 #
 # pylint: disable=bad-indentation,bad-continuation
 
-from __future__ import print_function
+
 import os
 import re
 import sys