Update osi_environment.proto

Co-authored-by: Pierre R. Mai <pmai@pmsf.de>
Signed-off-by: Clemens Linnhoff <clemens.linnhoff@persival.de>

Author: ClemensLinnhoff

osi_environment.proto

@@ -176,7 +176,7 @@ message EnvironmentalConditions
     // \par References:
     // [1] Shepard, F. D. (1996). <em>Reduced visibility due to fog on the highway.</em> Transportation Research Board, National Research Council (Ed.). National Academy Press. Washington, D.C., USA. ISBN 0-309-06006-0. \n
     // [2] Strassenverkehrs-Ordnung (StVO) as of dated  March 06, 2013 (BGBl. I S. 367), lastly changed by article 4a of the order from June 06, 2019 (BGBl. I S. 756). \n
-    // [3] StVO.de. (2013, April 01). <em>StVO Par. 17 Beleuchtung</em>. Retrieved January 25, 2020, from https://www.stvo.de/strassenverkehrsordnung/101-17-beleuchtung \n
+    // [3] stvo.de. (2013, April 01). <em>StVO Par. 17 Beleuchtung</em>. Retrieved January 25, 2020, from https://www.stvo.de/strassenverkehrsordnung/101-17-beleuchtung \n
     // [4] Meteorological Office UK. (2020). <em>Homepage of the Meteorological Office - How we measure visibility</em>. Retrieved January 25, 2020, from http://www.metoffice.gov.uk/guide/weather/observations-guide/how-we-measure-visibility
     //
     enum Fog