Set viewBox to "2 2 20 20" to trim 2px off each side of our
existing 24px icons, therefore aligning them to the new 20px
grid. All of them had been drawn with large margins, so none
of the graphic is lost.
Bug: T177432
Bug: T190151
Change-Id: Ifaa8c27450cde7ed25d4429bd8aba25bcba3bfcc