watchdog: update email address in conversion doc

The old one is defunct. However, I think it makes sense that I am still
the primary contact person for updates here.

Signed-off-by: Wolfram Sang <wsa@kernel.org>
Link: https://lore.kernel.org/r/20200502143103.19473-1-wsa@kernel.org


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