Update adwaita-icon-theme to 3.16.2.1

Use gtk3's gtk-update-icon-cache.

3.16.2
  - better metaphor for rotation allowed (bug #747117)
  - preferences-desktop-font for font-viewer
  - translations

3.16.0
  - translation updates

3.15.92
  - symbolic application-system
  - a11y icons for shell (bug #746022)
  - generic firmware mimetype icon

3.15.90
  - image manipulation action icons for symbolic (Photos)
  - less bulky folders
  - fullcolor mark location
  - grid alignment for some symbolics
  - translations

3.15.1
  - no hard dep on gtk-update-icon-cache (bug #739290)
  - missing icons needed for HC theme (bug #732511)
  - updated translations

(prlw1)