Remove the code to handle sid for resource map subproessor

[taojing2002]

Now, we made a decision that identifiers in resource map such as, documents, isDocumentedBy and so on, must be pids rather than sid. So we can clear the code to handle sids.

[taojing2002]

We also need to update the dataone documentation in this place:
https://dataoneorg.github.io/api-documentation/design/DataPackage.html#generating-resource-maps