MAINTAINERS: Remove Jia Liu

Jia Liu 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 Remove them, on the assumption that they are no longer active in QEMU. This makes the or1k-sim OpenRISC machine orphan. Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Message-id: 20260416091654.316158-18-peter.maydell@linaro.org