Updated description of proj_string

Author: PhilippHamerBMW

osi_groundtruth.proto

@@ -135,7 +135,7 @@ message GroundTruth
     // Projection string that allows to transform all coordinates in GroundTruth
     // into a different cartographic projection.
     //
-    // The string follows the proj.4 project rules [1].
+    // The string follows the PROJ.4 project rules for projections [1].
     //
     // \par References:
     // - [1] [Proj.4 Projections] (https://proj4.org/usage/projections.html)