TF-1973 Dispose ValueNotifier when not used

Signed-off-by: dab246 <tdvu@linagora.com>
(cherry picked from commit 10868d6ce1ed03bfd4736fbc3211296a5c62601b)

lib/features/thread/presentation/widgets/email_tile_web_builder.dart

@@ -628,4 +628,10 @@ class _EmailTileBuilderState extends State<EmailTileBuilder>  with BaseEmailItem
       );
     }
   }
+
+  @override
+  void dispose() {
+    _hoverNotifier.dispose();
+    super.dispose();
+  }
 }