.mailmap: redirect Philipp Tomsich Theobroma address to Vrull

The Theobroma address bounces as Philipp is not working there anymore,
so let's update with the one that seems to be working right now.

Cc: Philipp Tomsich <philipp.tomsich@vrull.eu>
Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de>