Mismatch between Restore shard steps and System collections

Description

1. At https://docs.mongodb.com/manual/tutorial/restore-sharded-cluster/index.html#remove-the-minoptimerecovery-document-from-the-admin-system-versions-collection it says "Remove the minOpTimeRecovery document from the admin.system.versions collection." but doesn't say why or what the minOpTimeRecovery document is. 

2. https://docs.mongodb.com/manual/reference/system-collections/#admin.system.version says "Stores the schema version of the user credential documents."

It doesn't seem that minOpTimeRecovery is about user credentials. So there may be changes or qualifications needed on both these pages.

Scope of changes

Impact to Other Docs

MVP (Work and Date)

Resources (Scope or Design Docs, Invision, etc.)