msglist: Remove trailingWhitespace

This 11px whitespace can be traced back to 311d4d5 in 2022, and is not
present in the Figma design. It was there to match the web design while
prototyping the app.

Author: PIG208

lib/widgets/message_list.dart

@@ -719,7 +719,6 @@ class _MessageListState extends State<MessageList> with PerAccountStoreAwareStat
         return MessageItem(
           key: ValueKey(data.message.id),
           header: header,
-          trailingWhitespace: 11,
           item: data);
     }
   }
@@ -1018,12 +1017,10 @@ class MessageItem extends StatelessWidget {
     super.key,
     required this.item,
     required this.header,
-    this.trailingWhitespace,
   });
 
   final MessageListMessageBaseItem item;
   final Widget header;
-  final double? trailingWhitespace;
 
   @override
   Widget build(BuildContext context) {
@@ -1036,7 +1033,6 @@ class MessageItem extends StatelessWidget {
         switch (item) {
           MessageListMessageItem() => MessageWithPossibleSender(item: item),
         },
-        if (trailingWhitespace != null && item.isLastInBlock) SizedBox(height: trailingWhitespace!),
       ]));
     if (item case MessageListMessageItem(:final message)) {
       child = _UnreadMarker(