Disable deprecation messages about onFoo connections (#534)

Signed-off-by: Addisu Z. Taddese <addisu@openrobotics.org>
Co-authored-by: Michael Carroll <michael@openrobotics.org>

src/Application.cc

@@ -99,6 +99,12 @@ Application::Application(int &_argc, char **_argv, const WindowType _type)
   this->setOrganizationDomain("gazebosim.org");
   this->setApplicationName("Gazebo GUI");
 
+  // Disable deprecation messages about onFoo connections since the new way of
+  // definining connections is only available as of Qt 5.12, which is not
+  // available in Ubuntu Focal
+  // TODO(azeey) Remove once Qt 5.12 is available in all supported platforms.
+  QLoggingCategory::setFilterRules("qt.qml.connections=false");
+
 #if __APPLE__
   // Use the Metal graphics API on macOS.
   gzdbg << "Qt using Metal graphics interface" << std::endl;