Remove unused import

Author: tze088

src/main/java/seedu/address/model/event/UniqueEventList.java

@@ -9,7 +9,6 @@
 import javafx.collections.ObservableList;
 import seedu.address.model.event.exceptions.DuplicateEventException;
 import seedu.address.model.event.exceptions.EventNotFoundException;
-import seedu.address.model.person.UniquePersonList;
 
 /**
  * A list of events that enforces uniqueness between its elements and does not allow nulls.