You are able to unassign a group from a Group Category at any time.
Changing/Removing a Group from a Group Category:
Click Groups or the People icon on the left menu.
Click the View button for the group you would like to adjust.
Click Settings near the top right. This will display the group’s settings page.
In the Basic Information section, click the Edit button.
Using the Group Category drop down, select a new Group Category. You could select No Category to have the group be assigned to no category or All to assign the group to all categories.
Click Save when done.