ENH: First pass through doxygen info updates for function objects

src/postProcessing/functionObjects/IO/removeRegisteredObject/removeRegisteredObject.H

@@ -21,6 +21,9 @@ License
     You should have received a copy of the GNU General Public License
     along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
 
+\addtogroup functionObjects
+@{
+
 Class
     Foam::removeRegisteredObject
 
@@ -30,6 +33,7 @@ Description
 SourceFiles
     removeRegisteredObject.C
     IOremoveRegisteredObject.H
+@}
 
 \*---------------------------------------------------------------------------*/