Rename authorization to authentication for --auth command line option to match --noauth and elsewhere

[reddog]

Compare https://docs.mongodb.com/manual/reference/program/mongod/#cmdoption-mongod-auth

--auth
Enables authorization to control user’s access to database resources and operations. When authorization is enabled, MongoDB requires all clients to authenticate themselves first in order to determine the access for the client.

with https://docs.mongodb.com/manual/reference/program/mongod/#cmdoption-mongod-noauth

--noauth
Disables authentication. Currently the default. Exists for future compatibility and clarity.

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This change is 

[reddog]

I got the terminology change the wrong way around! It should be authorization, see https://docs.mongodb.com/manual/reference/configuration-options/#security.authorization This means that the description for --noauth is the one that needs changing