autocomplete[nfc]: Remove duplicated code in refeshStaleUserResults

Author: Khader-1

lib/model/autocomplete.dart

@@ -312,15 +312,6 @@ class MentionAutocompleteView extends AutocompleteView<MentionAutocompleteQuery,
     // TODO test that logic (may involve detecting an unhandled Future rejection; how?)
     super.dispose();
   }
-
-  /// Recompute user results for the current query, if any.
-  ///
-  /// Called in particular when we get a [RealmUserEvent].
-  void refreshStaleUserResults() {
-    if (_query != null) {
-      _startSearch(_query!);
-    }
-  }
 }
 
 abstract class AutocompleteQuery {