Update the disabled-opa navbar icon size to reflect icon change

- The sizes of the button icons were shrunked, but opa layout (for the
  home button) scales the icon to another specified size which also
  needs to be updated

Fixes: 278011905
Test: go/nav-bar-icon-screenshot
Change-Id: Ieca803c3739adfa557ae8a5d20d28d9dd8511930