Made the event based risk demo faster by reducing the source model [skip CI]
Made the event based risk demo faster by reducing the source model [skip CI]


Former-commit-id: aec23cfb3d97961eaac63cd6e6d75d8c2c84cc94
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine