doc: fix lavapdu git url
doc: fix lavapdu git url

The repository is no longer in people/matthew.hart/

Change-Id: Ic46bca56051c4d59a35e119de86e140850b93f9b

Linaro/lava-server,Linaro/lava-server,OSSystems/lava-server,Linaro/lava-server,Linaro/lava-server,OSSystems/lava-server,OSSystems/lava-server