msmtp: upgrade 1.8.25 -> 1.8.26

msmtp: upgrade 1.8.25 -> 1.8.26

Changelog:
===========
- Add support for SCRAM-SHA-256-PLUS and SCRAM-SHA-1-PLUS authentication, and
  prefer SCRAM methods over the PLAIN method because of their superior
  properties.
- With --read-envelope-from, a Resent-From header is now used if it is present
  and appears before any From header

Signed-off-by: Wang Mingyu <wangmy@fujitsu.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>