v1.2.0: Document the change to three containers (#1581)
Beginning with the 22.06 release, the Merlin team provides the following three containers that are capable of training and inference: * `merlin-hugectr` * `merlin-tensorflow` * `merlin-pytorch` This is a change from the 22.05 release that used six containers--one for training and a separate container for inference. Remove step to install JupyterLab