MAINTAINERS: Remove Jianjun Wang as PCIe mediatek maintainer

MAINTAINERS: Remove Jianjun Wang as PCIe mediatek maintainer

Email to Jianjun Wang <jianjun.wang@mediatek.com> bounces with error:
"550 Relaying mail to jianjun.wang@mediatek.com is not allowed".
Remove the address to avoid sending future kernel maintenance queries
to an unreachable destination.

The MediaTek PCIe driver remains supported by Ryder Lee.

Signed-off-by: Hans Zhang <18255117159@163.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/20260515153635.136054-1-18255117159@163.com