comment: add depreceation comment for failedSMTPLogin email error message

Author: ip-qi

system/Language/en/Email.php

@@ -29,10 +29,11 @@
     'noSMTPAuth'            => 'Error: You must assign an SMTP username and password.',
     'invalidSMTPAuthMethod' => 'Error: SMTP authorization method "{0}" is not supported in codeigniter, set either "login" or "plain" authorization method',
     'failureSMTPAuthMethod' => 'Unable to initiate AUTH command. Your server might not be configured to use AUTH {0} authentication method.',
-    'failedSMTPLogin'       => 'Failed to send AUTH LOGIN command. Error: {0}',
     'SMTPAuthCredentials'   => 'Failed to authenticate user credentials. Error: {0}',
     'SMTPAuthUsername'      => 'Failed to authenticate username. Error: {0}',
     'SMTPAuthPassword'      => 'Failed to authenticate password. Error: {0}',
     'SMTPDataFailure'       => 'Unable to send data: {0}',
     'exitStatus'            => 'Exit status code: {0}',
+    // @deprecated
+    'failedSMTPLogin' => 'Failed to send AUTH LOGIN command. Error: {0}',
 ];