removed unnecessary fullcalendar plugin css file from demo

pages/calendar.html

@@ -12,7 +12,6 @@
   <link rel="stylesheet" href="https://code.ionicframework.com/ionicons/2.0.1/css/ionicons.min.css">
   <!-- fullCalendar -->
   <link rel="stylesheet" href="../plugins/fullcalendar/main.min.css">
-  <link rel="stylesheet" href="../plugins/fullcalendar-interaction/main.min.css">
   <link rel="stylesheet" href="../plugins/fullcalendar-daygrid/main.min.css">
   <link rel="stylesheet" href="../plugins/fullcalendar-timegrid/main.min.css">
   <link rel="stylesheet" href="../plugins/fullcalendar-bootstrap/main.min.css">