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.

changelog.d/1481-rio-transit.md

@@ -1,6 +1,5 @@
 - Add Rio de Janeiro to the Transit layer: municipal buses and the Mobi-Rio BRT
   from SMTR's keyless GTFS-Realtime feeds (CC BY 4.0), the layer's first Latin
-  American region. A feed that publishes speed in km/h declares
-  `speedUnit: 'kmh'` and the proxy converts it to m/s. Rio's internal route
-  keys are joined to SMTR's published GTFS `routes.txt`, so a card reads
-  "Route SN731" rather than "Route O0731AAN0A" (IMBrandao, #1481).
+  American region. Rio's internal route keys are joined to SMTR's published
+  GTFS `routes.txt`, so a card reads "Route SN731" rather than
+  "Route O0731AAN0A" (IMBrandao, #1481).