MAINTAINERS: Remove Wen Congyang

Wen Congyang has not posted to qemu-devel in some years and did not respond to a query about whether they still wished to be listed in our MAINTAINERS file. Remove them, on the assumption that they are no longer active in QEMU. Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Lukas Straub <lukasstraub2@web.de> Message-id: 20260416091654.316158-27-peter.maydell@linaro.org