DOC: Bad doxygen link

src/Cxx/Texture/ProjectedTexture.md

 ### Description
-vtkProjectedTexture  is tricky to set up. Picking the right parameters will take some iterations. The example uses vtkFrustum to help understand the parameters.
+vtkProjectedTexture  is tricky to set up. Picking the right parameters will take some iterations. The example uses vtkFrustumSource to help understand the parameters.
 
 !!! cite
     This example was inspired by Thomas Kilgus, German Cancer Research Center (DKFZ), Div. Medical and Biological Informatics, Junior group: Computer-assisted Interventions (E131), Im Neuenheimer Feld 280, 69120 Heidelberg, Germany