MAINTAINERS: update Senozhatsky email address

I don't check my @gmail.com addresses often enough these days.

Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210319054508.124762-1-senozhatsky@chromium.org