ps.1: Remove ambiguity in description of option '-J'

As stated in the previous commit, option '-J' was introduced by commit
"Add -J to filter by matching jail IDs and names."
(13767130c7, r265229), which unfortunately talked about '-J'
being a filter while actually implementing it as a regular selection
option which adds to the processes to display.

The manual page's formulation hinted more at '-J' being a filter, which
it is not, or could be just considered ambiguous, because of the
presence of the "only" word.  Consequently, remove it and reformulate.

Reviewed by:    ziaee, dch
MFC after:      1 day
Sponsored by:   The FreeBSD Foundation
Differential Revision:  https://reviews.freebsd.org/D50194

(cherry picked from commit cbda1aea65)

bin/ps/ps.1

@@ -35,7 +35,7 @@
 .\"
 .\"     @(#)ps.1	8.3 (Berkeley) 4/18/94
 .\"
-.Dd April 28, 2025
+.Dd May 06, 2025
 .Dt PS 1
 .Os
 .Sh NAME
@@ -285,7 +285,7 @@ of the jail.
 Use
 .Fl J
 .Sy 0
-to display only host processes.
+to request display of host processes.
 Implies
 .Fl x
 by default.