mod_sasl2_bind2, mod_sasl2_sm: Remove bind2 <features/> wrapper element
This was dropped from the spec. It's more consistent with SASL2.
---
summary: 'Anonymous unique occupant identifiers for MUCs'
...
Introduction
============
This module implements [XEP-0421: Anonymous unique occupant identifiers for
MUCs](https://xmpp.org/extensions/xep-0421.html).
TODO
====
- Subject messages
Compatibility
=============
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0.12 Built-in, not needed
0.11 Works; except in MUC-PMs
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