Invalidate MRs if LbMCSubmit update changes the stage 6 YAML
It would be nice to invalidate open merge requests if both:
- LbMCSubmit was updated
- the contents of the stage 6 YAML change
It'll need a little bit of thought about how to do this but it shouldn't be too difficult
Based on the discussion in https://mattermost.web.cern.ch/lhcb/pl/aowz9gzms7fxzg9zkgjf513o6h