kenv: s/dump/list/ to clarify meaning

The contents of the kenv will be dumped to stdout, while dump could have
also meant 'discard'. Call it 'list' instead.

Suggested by:	imp
Reviewed by:	imp, jhb
Differential Revision:	https://reviews.freebsd.org/D30836

bin/kenv/kenv.1

@@ -24,12 +24,12 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd October 5, 2020
+.Dd June 20, 2021
 .Dt KENV 1
 .Os
 .Sh NAME
 .Nm kenv
-.Nd dump or modify the kernel environment
+.Nd list or modify the kernel environment
 .Sh SYNOPSIS
 .Nm
 .Op Fl hNq
@@ -43,7 +43,7 @@
 .Sh DESCRIPTION
 The
 .Nm
-utility will dump the kernel environment if
+utility will list all variables in the kernel environment if
 invoked without arguments.
 If the
 .Fl h