Attributes : Remove bogus comment
Attributes : Remove bogus comment

This dates back to when Attributes derived from SceneElementProcessor, which it no longer does.

johnhaddon/gaffer,ImageEngine/gaffer,andrewkaufman/gaffer,hradec/gaffer,hradec/gaffer,ImageEngine/gaffer,johnhaddon/gaffer,GafferHQ/gaffer,GafferHQ/gaffer,johnhaddon/gaffer,GafferHQ/gaffer,ImageEngine/gaffer,hradec/gaffer,andrewkaufman/gaffer,GafferHQ/gaffer,hradec/gaffer,hradec/gaffer,johnhaddon/gaffer,andrewkaufman/gaffer,andrewkaufman/gaffer,GafferHQ/gaffer,ImageEngine/gaffer,johnhaddon/gaffer,andrewkaufman/gaffer