How Do I Remove the "Chapter #" Heading in the Word Output?

Answer

This is called a super heading and is control by a setting in the Topic. Removing the super heading will prevent it from appearing.

Normally, you will need to make this change to the template the Topic is based on. Once the template has been adjusted, any new Topics based on that template will not use this setting.

Note: Removing this field from the template tells Author-it "don't inherit" meaning the value is not inherited for any new Topics. This also means the field is not automatically removed from Topics already based on that template, as it can still be set at Topic level.
To find all Topics based on a template, select the Topic template, right-click and choose List Objects That Use This One. All Topics based on that template are listed, allowing you to open them and remove the field.