In D10107 I encountered a scenario where flow wasn't able to type check ServerLegacyRoleInfo as part of a ServerThreadInfo being constructed.
To be safe, I decided to look at all instances of ServerThreadInfo and fetchServerThreadInfos() in the codebase to double check for similar issues.
I didn't find any, but noticed that useKeyserverAdmin accepted ServerThreadInfo which seems strange. Looks like it was added when useKeyserverAdmin was getKeyserverAdmin. Regardless, it's no longer necessary so I removed it.
Depends on D10107