Make EC2 help output assertion a regex

This future proofs the test assertion in case "Amazon EC2" is
ever broken between two lines, similar to the rest of the test
cases.

tests/integration/test_cli.py

@@ -65,7 +65,7 @@ def test_help_output(self):
     def test_service_help_output(self):
         p = aws('ec2 help')
         self.assertEqual(p.rc, 0)
-        self.assertIn('Amazon EC2', p.stdout)
+        self.assertRegex(p.stdout, r'Amazon\s+EC2')
 
     def test_operation_help_output(self):
         p = aws('ec2 describe-instances help')