Fix another violation

Author: wendelinwemhoener

data/flashcard.txt

@@ -5,3 +5,4 @@ ddf | dfdf | - | - | -
 hello | bye | - | - | -
 hello | bye | - | - | -
 end program | hello | - | - | -
+d | d | - | - | -

src/main/java/seedu/duke/Duke.java

@@ -1,10 +1,7 @@
-//@@author wendelinwemhoener
-
 package seedu.duke;
 
 import seedu.duke.flashcard.Flashcard;
 import seedu.duke.flashcard.FlashcardComponent;
-import seedu.duke.calendar.Event;
 import seedu.duke.calendar.CalendarManager;
 
 import java.util.ArrayList;