package/msmtp: bump to version 1.8.6

package/msmtp: bump to version 1.8.6

>From the NEWS file:

Version 1.8.6:
- Aliases are now expanded recursively
- Minor bug fixes

Version 1.8.5:
- Fixed OAUTHBEARER.
- Support for TLS client certificates via PKCS11 devices, e.g. smart cards.
- Various small bug fixes and improvements.

Version 1.8.4:
- Added support for the OAUTHBEARER authentication method.
- Several minor bug fixes.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>