Remove Nomad-spark reference from use-cases.mdx
Remove Nomad-spark reference from use-cases.mdx

Removed ref to [Spark](https://github.com/hashicorp/nomad-spark) based on 
https://github.com/hashicorp/nomad-spark/commit/2c6092a2a6df6236282d2777e7de4a11c76f7cd6
hashicorp/nomad,burdandrei/nomad,burdandrei/nomad,dvusboy/nomad,hashicorp/nomad,burdandrei/nomad,dvusboy/nomad,hashicorp/nomad,dvusboy/nomad,hashicorp/nomad,hashicorp/nomad,burdandrei/nomad,burdandrei/nomad,dvusboy/nomad,hashicorp/nomad,dvusboy/nomad,dvusboy/nomad,burdandrei/nomad,dvusboy/nomad,burdandrei/nomad