fixed json syntax in biosample_cell_culture.json
fixed json syntax in biosample_cell_culture.json

hms-dbmi/fourfront,hms-dbmi/fourfront,4dn-dcic/fourfront,4dn-dcic/fourfront,hms-dbmi/fourfront,hms-dbmi/fourfront,4dn-dcic/fourfront,4dn-dcic/fourfront,hms-dbmi/fourfront