SERVER-41697 strips out the 'ns' field for the indexes of a namespace when the server is on FCV 4.4 and that namespace undergoes a DDL operation. This means that namespaces that didn't see any DDL operations in their 4.4 lifetime will be left with a stray 'ns' field in their index specifications once the cluster upgrades to more recent versions.

This ticket is to explore a catch-all solution to remove all 'ns' fields from the index specifications.