gitk: Mention globs in description of preference to hide custom refs

This clarifies that one has to enter e.g. `jj/keep/*` and not just
`jj/keep`.

Follows up on 2441e19.

Signed-off-by: Ilya Grigoriev <ilyagr@users.noreply.github.com>

Author: ilyagr

gitk

@@ -11683,7 +11683,7 @@ proc prefspage_general {notebook} {
 
     ttk::entry $page.refstohide -textvariable refstohide
     ttk::frame $page.refstohidef
-    ttk::label $page.refstohidef.l -text [mc "Refs to hide (space-separated)" ]
+    ttk::label $page.refstohidef.l -text [mc "Refs to hide (space-separated globs)" ]
     pack $page.refstohidef.l -side left
     pack configure $page.refstohidef.l -padx 10
     grid x $page.refstohidef $page.refstohide -sticky ew