fix warning about missing one-line description during packaging

Index: slurm.1
--- slurm.1.orig
+++ slurm.1
@@ -4,6 +4,7 @@
 .\"
 .Sh NAME
-slurm \- yet another network load monitor
+.Nm slurm
+.Nd yet another network load monitor
 .Sh SYNOPSIS
 .Nm slurm
 .Op Fl hHz
