Fix --resetaccount not clearing Duo 2FA (missing delete keyword) (#7797)
Follow-up to commit 1399ce35 ("forgot 2 extra otpduo to clear!"), which added otpduo cleanup in two places. The meshuser.js side correctly used `delete chguser.otpduo;`. The meshcentral.js --resetaccount path got `user.otpduo;` instead of `delete user.otpduo;` -- the `delete` keyword was lost. As a bare expression statement it has no effect. Effect: an administrator running --resetaccount to unlock a user that has Duo 2FA configured will see all other 2FA fields cleared, but the Duo record on the user document survives. On next login the server still requires Duo authentication, defeating the account-recovery purpose. Related historical reports of --resetaccount not clearing specific 2FA mechanisms: #3455 (original "not clearing 2 factor"), #5310 (ntfy variant), #5331 (messaging cleanup PR).