Run GWSkyNet tasks on openmp queue

Originally, we allocated a dedicated queue for GWSkyNet tasks because they needed a lot of memory and because they used many CPUs and the flavor of parallelism was poorly understood (#514 (closed)).

Their memory usage is now greatly reduced by using multi-resolution sky maps and the flavor of parallelism is now well understood as resulting from OpenMP usage in ligo.skymap volume rendering (manleong.chan/gwskynet#5 (closed)).

It is now safe to reallocate GWSkyNet tasks to the workers that we have dedicated for OpenMP parallel workflows. This patch directs GWSkyNet tasks to the openmp queue and retires the now unnecssary skynet queue. This simplifies deployment while also reducing resource requirements, both on the cluster and in Kubernetes development setups.

There is a FIXME comment noting that even the high CPU usage stemming from the OpenMP-parallel volume rendering may eventually be unnecessary (see manleong.chan/gwskynet#6).