There is a way to workaround and remove the Maturity field, but you should know that this will remove it from all projects. In the StoryDetails.cshtml file
C:\Program Files (x86)\Telerik\TeamPulse\wwwroot\Areas\View\Views\DetailsTemplates\StoryDetails.cshtml
Remove the maturity section
@Html.DisplayFor(x => x[Constants.Maturity], "WorkItemField")
@Html.EditorFor(x => x[Constants.Maturity], "WorkItemField")
This workaround would not be suitable, in case you need to hide it only from one project.