Changes to On-demand GitHub source materialization

the response property releases/items/publishedAt became nullable for the status 200

the response property releases/items/url became nullable for the status 200

the response property releases/items/version became nullable for the status 200

the response property source/isHidden became nullable for the status 200

the response property source/metadata became nullable for the status 200

the response property source/orgId became nullable for the status 200

the response property source/productId became nullable for the status 200

the response property source/starsFetchedAt became nullable for the status 200

response property releases/items/publishedAt list-of-types was narrowed by removing types null from media type application/json of response 200

response property releases/items/url list-of-types was narrowed by removing types null from media type application/json of response 200

response property releases/items/version list-of-types was narrowed by removing types null from media type application/json of response 200

response property source/isHidden list-of-types was narrowed by removing types null from media type application/json of response 200

response property source/metadata list-of-types was narrowed by removing types null from media type application/json of response 200

response property source/orgId list-of-types was narrowed by removing types null from media type application/json of response 200

response property source/productId list-of-types was narrowed by removing types null from media type application/json of response 200

response property source/starsFetchedAt list-of-types was narrowed by removing types null from media type application/json of response 200

added the new too_large enum value to the error/type response property for the response status 400