Cleanup: remove redundant doxygen \file argument

Move \ingroup onto same line to be more compact and
make it clear the file is in the group.

source/blender/python/generic/bgl.c

@@ -14,8 +14,7 @@
  * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  */
 
-/** \file blender/python/generic/bgl.c
- *  \ingroup pygen
+/** \file \ingroup pygen
  *
  * This file is the 'bgl' module which wraps OpenGL functions and constants,
  * allowing script writers to make OpenGL calls in their Python scripts.