Remove GeometryType section from Doxygen documentation

The section is empty since the code was split into the dune-geometry
module.

(cherry picked from commit c37cd9cb)
Signed-off-by: Steffen Müthing <muething@dune-project.org>

dune/common/modules.txt

@@ -7,8 +7,3 @@
 
    Only @addtogroup is used in the code documentation.
 */
-
-  /**
-   * @defgroup COGeometryType GeometryType
-   * @ingroup Common
-  */