dt-bindings: ltk050h3146w: replace Heiko Stuebner by myself as maintainer

Heiko does not work at Theobroma Systems anymore and the boards using
those panels are downstream, maintained internally by the company, so
let's relieve Heiko of maintainership duties.

Cc: Heiko Stuebner <heiko@sntech.de>
Cc: Quentin Schulz <foss+kernel@0leil.net>
Signed-off-by: Quentin Schulz <quentin.schulz@theobroma-systems.com>
Acked-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220131165439.717713-1-quentin.schulz@theobroma-systems.com