Remove old database migrations in SyncServer

[crspybits]

From the server logs:

[2018-12-12T03:52:19.907Z] [INFO] [Database.swift:134 columnExists(:in:)] Column updateDate was already in database table Upload
[2018-12-12T03:52:19.910Z] [INFO] [Database.swift:138 columnExists(:in:)] Column cloudFolderName was not in database table Upload
[2018-12-12T03:52:19.911Z] [INFO] [Database.swift:134 columnExists(:in:)] Column appMetaDataVersion was already in database table Upload
[2018-12-12T03:52:19.912Z] [INFO] [Database.swift:134 columnExists(:in:)] Column fileGroupUUID was already in database table Upload
[2018-12-12T03:52:19.914Z] [INFO] [Database.swift:104 createTableIfNeeded(tableName:columnCreateQuery:)] Table FileIndex was already in database
[2018-12-12T03:52:19.915Z] [INFO] [Database.swift:134 columnExists(:in:)] Column creationDate was already in database table FileIndex
[2018-12-12T03:52:19.917Z] [INFO] [Database.swift:134 columnExists(:in:)] Column updateDate was already in database table FileIndex
[2018-12-12T03:52:19.918Z] [INFO] [Database.swift:138 columnExists(_:in:)] Column cloudFolderName was not in database table FileIndex

I think the cloudFolderName columns are being spuriously added. Plus, I think this migration code for columns can just be removed.