Fix memory leak in VTKRenderer
vtkMatrix4x4* vtkCamera::GetProjectionTransformMatrix(vtkRenderer* ren)
returns an owning pointer. By not deleting the pointer there was a memory leak caught by vtkDebugLeaks.
Note: vtkMatrix4x4* vtkCamera::GetProjectionTransformMatrix(double aspect, double nearz, double farz)
returns a non-owning pointer and there is no mention of the difference in the VTK documentation.
I opened an issue in VTK requesting updated documentation on this (vtk/vtk#18386).