Fix layout-padding css

Adds a `,` which was missing in 5caa22b2c444485b3d340cda662d8808b1fc381d when `layout-padding` was readded. Also removes a comment saying `layout-padding` is depreciated since it has been readded.
It appears that @ajoslin removed the whole rule in https://github.com/angular/material/commit/d3577798c7384a003f0fa548e948c6201e86491d :)