PixelPaint: Don't const_cast to update the editor on filter application

Author: https://github.com/Zaggy1024
Commit: https://github.com/SerenityOS/serenity/commit/ba236e3f21
Pull-request: https://github.com/SerenityOS/serenity/pull/20389
Reviewed-by: https://github.com/BertalanD ✅

Userland/Applications/PixelPaint/ImageProcessor.cpp

@@ -30,8 +30,7 @@ void FilterApplicationCommand::execute()
     }
 
     m_filter->m_editor->gui_event_loop().deferred_invoke([strong_this = NonnullRefPtr(*this)]() {
-        // HACK: we can't tell strong_this to not be const
-        (*const_cast<NonnullRefPtr<Layer>*>(&strong_this->m_target_layer))->did_modify_bitmap(strong_this->m_target_layer->rect());
+        strong_this->m_target_layer->did_modify_bitmap(strong_this->m_target_layer->rect());
         strong_this->m_filter->m_editor->did_complete_action(DeprecatedString::formatted("Filter {}", strong_this->m_filter->filter_name()));
     });
 }