Fix version number when saving events/todos.

src/pim-types.ts

@@ -51,7 +51,7 @@ export class EventType extends ICAL.Event implements PimType {
   public toIcal() {
     const comp = new ICAL.Component(['vcalendar', [], []]);
     comp.updatePropertyWithValue('prodid', '-//iCal.js EteSync Web');
-    comp.updatePropertyWithValue('version', '4.0');
+    comp.updatePropertyWithValue('version', '2.0');
 
     comp.addSubcomponent(this.component);
     if (this.timezoneComp) {