Remove documentation that KubernetesProvider job_name must be unique (#…

…3506)

The job_name is uniquified with a timestamp inside the submit method,
and the default job_name is "parsl", which is not unique wrt other
invocations using the default.

parsl/providers/kubernetes/kube.py

@@ -168,7 +168,7 @@ def submit(self, cmd_string, tasks_per_node, job_name="parsl"):
              - tasks_per_node (int) : command invocations to be launched per node
 
         Kwargs:
-             - job_name (String): Name for job, must be unique
+             - job_name (String): Name for job
 
         Returns:
              - job_id: (string) Identifier for the job