erlang-stun: Update to 1.2.6

upstream changes:
-----------------
Version 1.2.6
  o Updating fast_tls to version 1.1.16.
  o Increase receive timeout
Version 1.2.5
  o Hand over error events to callback function.
  o Improve TCP/TLS performance if no traffic shaper is configured.
Version 1.2.4
  o Improve handling of invalid REQUESTED-ADDRESS-FAMILY value.
  o Apply minor logging improvements.
  o Reopen listener sockets if they were closed.
Version 1.2.3
  o Don't complain about proxy_protocol option.
  o Gracefully handle errors while receiving UDP data.
  o Reduce log level of errors that may occur during normal operation.
  o Restart listeners on failure.
Version 1.2.2
  o Updating fast_tls to version 1.1.15.
  o Updating p1_utils to version 1.0.25.
Version 1.2.1
  o Updating fast_tls to version 1.1.14.
  o Updating p1_utils to version 1.0.23.
  o Include 'SOFTWARE' attribute in responses.
  o Use random session IDs.
Version 1.2.0
  o Allow for whitelisting IP addresses/subnets.
  o Accept expired credentials for TURN session refreshes.
  o Accept additional TLS options/ciphers.
Version 1.1.0
  o Support the HAproxy protocol (v1 and v2).
  o Don't close listener if accepting a connection fails.
  o Only use new 'socket' backend for multiplexing TCP/TLS listeners.
Version 1.0.47
  o Disable new 'socket' backend for TCP/TLS connections on Windows.
Version 1.0.46
  o Use new 'socket' backend for TCP/TLS connections (on Erlang/OTP 23+).
  o Support multiplexing TCP/TLS listeners (on Erlang/OTP 23+).
Version 1.0.45
  o Improve UDP receive performance.
  o Reduce risk of UDP packet loss.
  o Support multiple passwords to facilitate rollover.
Version 1.0.44
  o Updating fast_tls to version 1.1.13.
  o Updating p1_utils to version 1.0.23.
  o Switch from using Travis to Github Actions as CI

(triaxx)