TrigUpgradeTest: remove runMenuTest and fix RootComp step
Two minor changes in TrigUpgradeTest:
- Remove obsolete runMenuTest (script, job opts and reference) - it has been long replaced by the full_menu_build test (ATR-19845).
- Skip RootComp step in case both expert-monitoring.root and the reference are missing, as it is then most likely that a given test simply doesn't produce one. This closes ATR-20105.