If you are planning on upgrading to Moodle 3.5 later this year, then you will need to update Base theme that you have in the 3.1 version.
The quickest way, I think, would be is to use CSS in order to remove the unwanted duplicated heading.
Trouble is that I’m not sure what that CSS should be, as I don’t have a Moodle 3.1 site now.