Removed redundancy in QGraphicsItem documentation.

Snippets [1] and [QGraphicsItem type] are the exact same, each
referenced once, and only in the same file.  Removed the later snippet.

Change-Id: I4f35a8322034b00e9b5f5d6c6d96e652f11f8384
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Fixed small bug in code snippet for QGraphicsItem

If the enumeration "Type" isn't declared in the public scope, it will
cause an issue upon compilation.  Previously, it was ambiguous on which
access level this should be in.  Snippet [18] though has the enumeration
in the correct access level.

Change-Id: If699df80def3e1b09d8d82df74c4ca85eba003d2
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>