itinerary: 'mousewheel' handler calling stopPropagation breaks scroll in Firefox

[DennisOSRM]

Description:
The itinerary control adds a 'mousewheel' listener that calls L.DomEvent.stopPropagation(e), which in Firefox can cause the page to zoom instead of letting the directions pane scroll.

Reproduction:

1. Open https://map.project-osrm.org/
2. Click two locations to create a route
3. Attempt to scroll the directions list with mouse wheel in Firefox — page zooms instead of the list scrolling.

Suggested fix:
Replace the explicit 'mousewheel' handler with L.DomEvent.disableScrollPropagation(this._container) so Leaflet handles cross-browser 'wheel' events correctly.

References:

• OSRM issue: Scrolling list of instructions with mouse wheel is broken Project-OSRM/osrm-frontend#195
• Mozilla bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1942589

Thanks!