fix(return): do not pull up parent's margin bottom for segments.

Fixing issue:
      if(order == null) {
        @return
        SGW->Client:401
      }

src/components/DiagramFrame/SeqDiagram/MessageLayer/Block/Statement/Return/Return.vue

@@ -117,7 +117,7 @@ export default {
 </script>
 
 <style scoped>
-.statement-container:last-child > .interaction.return {
+.occurrence > .block > .statement-container:last-child > .interaction.return {
   /* It pulls up the parent's (.statement-container) bottom margin. */
   margin-bottom: -16px;
   bottom: -2px; /* The width of the border of the Occurrence */