Remove source_url from data_sources_documents

[philipperolet]

Depends on #9950

• compare source_url from documents and nodes to ensure that if document has a source_url, it's the same as node (otherwise, fine)
• read source_url from nodes, not from documents --- ensure document's source_url isn't used anywhere
• after a day or 2, drop the column from documents, removing the writes and reads from this column

[philipperolet]

Careful to watch for all the times source_url is grabbed from documents --- it should be grabbed from nodes there, e.g. here