MaxCUWidth and MaxCUHeight config parameters

[jani.lainema]

MaxCUWidth and MaxCUHeight encoder configuration parameters don't seem to have effect even though present in the default VTM configuration files. It looks like the functionality of these two is overwritten by the CTUSize parameter. MaxCUWidth is however referred to if compiling VTM with ENABLE_QPA_SUB_CTU set to 0, but probably the same functionality could be achieved using CTUSize instead.

There is comment relating to CTUSize parameter saying: "specifies the CTU size if QTBT is on". That may indicate the MaxCUWidth and MaxCUHeight parameters are leftovers from pre-QTBT time. Or are those still intended to be used if disabling some QTBT functionality?