What is hosted service endpoints?

The hosted service was a centralized service that used to host all of the subgraphs on The Graph. It has been sunset recently and now all of the subgraphs are on the decentralized network (and can be seen here: https://thegraph.com/explorer)

The hosted service was effectively a giant centralized single indexer node in the cloud that was responsible for 'hosting' all of the subgraphs that people made to index their own blockchain data. Now, the hosted service doesn't exist and so you cannot 'publish' your subgraphs to it. Instead, you will have to 'publish' your subgraphs to the decentralized network of many indexer nodes.