Change Public studies API to reinstate is published flag

[sajo-ebi]

Sumstats FTP sync is failing is because of accession Id being null returned from Public studies API , we had changed API to return all studies instead of isPublished flag as true, this is causing sumsats sync to fail , we have to reinstate the changes. The ticket for the issue is -:

https://app.zenhub.com/workspaces/gwas-59df823c4a6feb3786810391/issues/gh/ebispot/goci/1084