fix(transit): read Rio speeds as the m/s SMTR publishes

Both SMTR feeds now publish Position.speed in m/s. Compared with how far
vehicles moved between reports on 2026-11-05, the published values ran
3.1x (buses) and 3.6x (BRT) below the observed speed, so the km/h
conversion divided real speeds by 3.6. Drop speedUnit and the conversion.

docs/CURRENT-STATE.md

@@ -4649,8 +4649,7 @@ Helsinki, the Netherlands, Norway, South East Queensland, Rio de Janeiro
 (municipal buses and the Mobi-Rio BRT, two feeds), and nine in
 Ontario — Toronto (TTC surface vehicles; the subway publishes no
 positions), MiWay, Hamilton HSR, Durham Region, YRT/Viva, Guelph,
-Burlington, Barrie and Kingston. Rio's feeds publish speed in km/h, which
-the proxy converts to m/s before any card reads it. Mode silhouettes
+Burlington, Barrie and Kingston. Mode silhouettes
 identify buses, trams, subways, trains, ferries and unclassified vehicles.
 
 Retained transit history uses the same outlier quarantine as live observations and