Display the Group Title after the content in Views Grouped By
You should override the views-view-grid.tpl.php for your views. Otherwise, it will be effect all grid layout into your site. 

The correct template suggestions for views be views-view-grid--[views_name].tpl.php or views-view-grid--[views_name]--[display_id].tpl.php.

To know more template suggestions for views, you can follow below step.


Go to Administration » Structure » Views
Edit your views 
Open the correct display of the views.
Click on  information link for theme under Advanced tab.
A popup be display for all template suggestions for a particular
views.