560 start node shouldnt have an input node - update

[vin-ni]

Forgot to commit the last update.
Sorry

[github-actions]

File	Coverage
All files	82%	✅
gencaster/db_logging.py	96%	✅
gencaster/distributor.py	68%	✅
gencaster/schema.py	59%	✅
gencaster/urls.py	76%	✅
osc_server/models.py	91%	✅
osc_server/server.py	55%	✅
story_graph/engine.py	91%	✅
story_graph/markdown_parser.py	91%	✅
story_graph/models.py	96%	✅
story_graph/types.py	93%	✅
stream/frontend_types.py	94%	✅
stream/models.py	92%	✅
stream/types.py	99%	✅

Minimum allowed coverage is 50%

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