autocomplete [nfc]: Delete wildcard and user group autocomplete result classes

The WildcardMentionAutocompleteResult and
UserGroupMentionAutocompleteResult classes are not
used, so better to remove them for now.

Author: sm-sayedi

lib/model/autocomplete.dart

@@ -342,21 +342,6 @@ class UserMentionAutocompleteResult extends MentionAutocompleteResult {
   final int userId;
 }
 
-enum WildcardMentionType {
-  all,
-  everyone,
-  stream,
-}
-
-class WildcardMentionAutocompleteResult extends MentionAutocompleteResult {
-  WildcardMentionAutocompleteResult({required this.type});
-
-  final WildcardMentionType type;
-}
+// TODO(#233)
 
-
-class UserGroupMentionAutocompleteResult extends MentionAutocompleteResult {
-  UserGroupMentionAutocompleteResult({required this.userGroupId});
-
-  final int userGroupId;
-}
+// TODO(#234)

lib/widgets/autocomplete.dart

@@ -107,10 +107,6 @@ class _ComposeAutocompleteState extends State<ComposeAutocomplete> with PerAccou
         // TODO(i18n) language-appropriate space character; check active keyboard?
         //   (maybe handle centrally in `widget.controller`)
         replacementString = '${mention(store.users[userId]!, silent: intent.query.silent, users: store.users)} ';
-      case WildcardMentionAutocompleteResult():
-        replacementString = '[unimplemented]'; // TODO(#234)
-      case UserGroupMentionAutocompleteResult():
-        replacementString = '[unimplemented]'; // TODO(#233)
     }
 
     widget.controller.value = intent.textEditingValue.replaced(
@@ -128,10 +124,6 @@ class _ComposeAutocompleteState extends State<ComposeAutocomplete> with PerAccou
       case UserMentionAutocompleteResult(:var userId):
         // TODO(#227) avatar
         label = PerAccountStoreWidget.of(context).users[userId]!.fullName;
-      case WildcardMentionAutocompleteResult():
-        label = '[unimplemented]'; // TODO(#234)
-      case UserGroupMentionAutocompleteResult():
-        label = '[unimplemented]'; // TODO(#233)
     }
     return InkWell(
       onTap: () {