Change announcements to be collapsed on page load in web UI (#12990)

app/javascript/mastodon/features/getting_started/components/announcements.js

@@ -376,7 +376,7 @@ class Announcements extends ImmutablePureComponent {
         <img className='announcements__mastodon' alt='' draggable='false' src={mascot || elephantUIPlane} />
 
         <div className='announcements__container'>
-          <ReactSwipeableViews animateHeight index={index} onChangeIndex={this.handleChangeIndex}>
+          <ReactSwipeableViews animateHeight={!reduceMotion} adjustHeight={reduceMotion} index={index} onChangeIndex={this.handleChangeIndex}>
             {announcements.map(announcement => (
               <Announcement
                 key={announcement.get('id')}