css: specifying `max-height` and `overflow-y` for `.nteract-cell-outputs.expanded` cells
css: specifying `max-height` and `overflow-y` for `.nteract-cell-outputs.expanded` cells

fixes https://github.com/nteract/nteract/issues/5132.

original context: https://github.com/nteract/nteract/pull/5113#issuecomment-636254454

nteract/nteract,nteract/composition,nteract/nteract,nteract/nteract,nteract/nteract,nteract/composition,nteract/nteract,nteract/composition