fix: do not create south road twice on unlink

- this was changed from else if to if in 7623698a00 (diff-b05df598e90ce5418467b07e84ef85a80be8bac7c70929063ace9ede4d5cf52eL1000) (for unknown reason)
 - fixes #4704

Core/src/main/java/com/plotsquared/core/plot/PlotModificationManager.java

@@ -371,8 +371,7 @@ public final class PlotModificationManager {
                             manager.createRoadSouthEast(current, queue);
                         }
                     }
-                }
-                if (current.isMerged(Direction.SOUTH)) {
+                } else if (current.isMerged(Direction.SOUTH)) {
                     manager.createRoadSouth(current, queue);
                 }
             }