net-im/prosody: Update to 0.11.3

Changelog:

https://blog.prosody.im/prosody-0.11.3-released/

PR: 241488
Submitted by: Thomas Morper <thomas beingboiled info>
Approved by: portmgr (maintainer timeout: > 1 month)
MFH: 2020Q1 (blanket: bugfix release)