Tidy up documentation

Based on PR feedback.

Signed-off-by: Caspar de Haes <caspar.dehaes@five.ai>

Author: caspar-ai

osi_object.proto

@@ -341,8 +341,8 @@ message MovingObject
     // The trajectory that this moving object expects to follow in the future.
     //
     // This is not externally perceivable information, rather this is to aid
-    // realistic simulation of agents not under test.  This information should
-    // not be made available to the stack under test.
+    // realistic simulation of traffic participants not under test.  This
+    // information should not be made available to the stack under test.
     //
     // \note Moving objects are not required to stick to this trajectory, it is
     // indicative, and equivalent to the output of a perception + prediction

osi_trafficupdate.proto

@@ -40,10 +40,10 @@ message TrafficUpdate
 
     // Updated traffic participant data
     //
-    // \note Only the id, base member (without dimension and base_polygon),
-    // and the vehicle_classification.light_state members are considered in
-    // updates, all other members can be left undefined, and will be
-    // ignored by the receiver of this message.
+    // \note It is not expected that static fields are populated, and if they
+    // are they may be ignored by the receiver of this message (e.g. dimensions,
+    // or vehicle category).  All dynamic fields should be populated where known
+    // for example, velocity, light states, or future trajectory.
     //
     repeated MovingObject traffic = 3;
 }