Revert "Add SVG versions of toolbar icons"

There were issues with shadows, and the sprite creating weird
offsetted buttons on Chrome.
Subsequent attempts have been incomplete at solving these, so
reverting this and hoping that the next person to attempt a conversion
to SVG is more successful.

This reverts commit e027051c58a8e76b1d254fde8ed62421f3740f32.

Bug: 35342
Change-Id: Id296899a2c3746957c17068ab17ca8266f6ff0d3