UI: simplify ui_draw_vision_speed (#19594)
UI: simplify ui_draw_vision_speed (#19594)

* simplify draw_vision_speed

* use std::nearbyint

* use std::to_string
commaai/openpilot,commaai/openpilot,commaai/openpilot,commaai/openpilot,commaai/openpilot,commaai/openpilot