mailmap: add entry for obsolete email address

Map old corporate email address @yandex-team.ru to stable private address.

Signed-off-by: Konstantin Khlebnikov <koct9i@gmail.com>
Link: https://lore.kernel.org/r/159360469186.24918.10108157093572183535.stgit@zurg


Signed-off-by: Jonathan Corbet <corbet@lwn.net>