Ummmm, are you sure it has been applied? Or has it been reverted in the meantime? Because I’m not seeing it.
This is what I see currently (even after numerous force-refreshes):
And this is what I think I’m supposed to be seeing (if this CSS change was really implemented):
(Note that I’m changing max-width in Developer Tools, as width seems to be auto-calculated to preserve aspect ratio - at current version of the community.osm.org website?)