doc: drop core version warnings from admin guide

Problem: the admin guide calls out warnings against specific flux-core
version limitations, but when the admin guide is a part of flux-core,
its warnings obviously apply to the current version.

Drop the flux-core version numbers.  They are out of date anyway.

Author: garlick

doc/guide/admin.rst

@@ -12,12 +12,8 @@ resource manager on a cluster.
     Flux is still beta software and many of the interfaces documented
     in this guide may change with regularity.
 
-    This document is in DRAFT form and currently applies to flux-core
-    version 0.50.0.
-
 .. warning::
-    0.50.0 limitation: the flux system instance is primarily tested on
-    a 128 node cluster.
+    The Flux system instance is primarily tested on a 128 node cluster.
 
 
 ***********************
@@ -590,7 +586,7 @@ enabled.
 Adding Job Prolog/Epilog Scripts
 ================================
 
-As of 0.50.0, Flux does not support a traditional job prolog/epilog
+Flux does not currently support a traditional job prolog/epilog
 which runs as root on the nodes assigned to a job before/after job
 execution. Flux does, however, support a job-manager prolog/epilog,
 which is run at the same point on rank 0 as the instance