Add comments to clarify minQT size for chroma separate tree is in chroma samples

cfg/encoder_intra_vtm.cfg

cfg/encoder_lowdelay_P_vtm.cfg

cfg/encoder_lowdelay_vtm.cfg

cfg/encoder_randomaccess_vtm.cfg

...nfigExamples/encoder_randomaccess_vtm_RasterScanSlice.cfg

...figExamples/encoder_randomaccess_vtm_RectangularSlice.cfg

...es/encoder_randomaccess_vtm_RectangularSliceFixedSize.cfg

...gExamples/encoder_randomaccess_vtm_SingleTilePerSlice.cfg

source/Lib/DecoderLib/VLCReader.cpp

source/Lib/EncoderLib/VLCWriter.cpp