Remove dead code

The code in question [has been moved][1] to [another `handle_info/3` clause][2].

[1]: https://github.com/processone/ejabberd/commit/9deb294328bb3f9eb6bd2c0e7cd500732e9b5830
[2]: https://github.com/processone/ejabberd/blob/6baf3a24de429ed6cf27b267d5b91ef3d64114bf/src/ejabberd_c2s.erl#L1361