http_caldav_sched.c don't add timezone data

We removed this line quite some time ago in Fastmail builds, because we
sometimes saw downstream problems with Exchange.

Ken Murchison's advice was that in general clients should not (or no
longer) be looking at TZ data included in events, anyway.  Adding it
could cause problems, but probably helps no one.  Instead, we'll just
leave it be.

(This commit message was written by Ricardo Signes, replacing the
previous internal Fastmail commit message.  The code change is by Bron
Gondwana.)

imap/http_caldav_sched.c

@@ -1160,8 +1160,6 @@ static void sched_deliver_remote(const char *cal_ownerid, const char *sched_user
 
     syslog(LOG_DEBUG, "sched_deliver_remote(%s, %X)", recipient, sparam->flags);
 
-    icalcomponent_add_required_timezones(sched_data->itip);
-
     if (sparam->flags & SCHEDTYPE_ISCHEDULE) {
         /* Use iSchedule */
         xmlNodePtr xml;