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
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:1709864c4883f54397afb0f4b819b5a90c9e2055)
Merged-In: Ieca803c3739adfa557ae8a5d20d28d9dd8511930
Change-Id: Ieca803c3739adfa557ae8a5d20d28d9dd8511930