Generator metatag not removed in maintenance mode

Problem/Motivation

This module removes the generator metatag by default. But the generator metatag is not removed when the site is in maintenance mode.

Steps to reproduce

1. Install site and module
2. View source and confirm generator metatag is gone
3. Set site to maintenance mode
4. View source and observe generator metatag remains

Tested with a vanilla install on simplytest.me.