fix(docs): Remove stray line (#465)

Signed-off-by: Maximilian Rosin <maximilian.rosin@parson-europe.com>

Author: max-rosin

osi_common.proto

@@ -219,7 +219,6 @@ message Identifier
 //
 // The external reference is an optional recommendation to refer to objects defined outside of OSI.
 // This could be other OpenX standards, 3rd-party standards or user-defined objects.
-// simulation environments.
 //
 // \note ExternalReference is optional and can be left empty.
 //