In commit 55c3c7987 we updated the admin layout header to use
`class="dropdown menu" data-dropdown-menu` instead of `class="menu"
data-responsive-menu="medium-dropdown"`.
Then, in commit dcec003d0, we updated the public layout header to use
`class="menu" data-responsive-menu="medium-dropdown"` instead of
`class="dropdown menu" data-dropdown-menu`.
Now we're applying the same classes to both, hoping we can get some
consistent styles.
I'm choosing to keep the ones in the public layout because using it I
had less problems when trying to improve the styles of this navigation.