Update osi_object.proto

Co-authored-by: Stefan Cyliax <stefan.cyliax@asam.net>

Author: pmai

osi_object.proto

@@ -680,7 +680,7 @@ message MovingObject
             // If different friction coefficients due to more than one contact points are available,
             // this value contains the average.
             //
-            // Unit: Dimensionless.
+            // Unit: Dimensionless
             //
             // \par References:
             // [1] Britannica, T. Editors of Encyclopaedia. (2020, June 24). <em>coefficient of friction</em>. Retrieved May 18, 2022, from https://www.britannica.com/science/coefficient-of-friction