ptcloud: fix viz3d build without OpenGL

Close the cv::viz3d namespaces outside the trailing #ifdef HAVE_OPENGL
block. Previously the closing braces were inside the guard, so a build
with OpenGL disabled dropped them and failed with
'expected }' at end of input'.

modules/ptcloud/src/viz3d/viz3d.cpp

@@ -1534,7 +1534,7 @@ void PointCloud::setShader(ogl::Program program_)
     this->proj_loc = this->program.getUniformLocation("proj");
 }
 
+#endif // HAVE_OPENGL
+
 } // namespace viz3d
 } // namespace cv
-
-#endif