doc: include missing doc file
doc: include missing doc file

The file lava-scheduler-job.rst was not included by any documents.

Change-Id: I75cfae2ef7805c9ec1225cf39057eeb052b63731

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