[polari] userList: Replace Gtk.Arrow

[Florian Müllner <fmuellner src gnome org>]

commit 90525166ba28c80e3a9b4ff1af4acc670a688c39
Author: Florian Müllner <fmuellner gnome org>
Date:   Fri Oct 9 14:38:37 2020 +0200

    userList: Replace Gtk.Arrow
    
    It is deprecated and will be removed in GTK4.
    
    Just use an appropriate image.
    
    https://gitlab.gnome.org/GNOME/polari/-/merge_requests/174

 src/userList.js | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)
---
diff --git a/src/userList.js b/src/userList.js
index ea320eab..2c6056ca 100644
--- a/src/userList.js
+++ b/src/userList.js
@@ -469,8 +469,8 @@ class UserListRow extends Gtk.ListBoxRow {
             margin_bottom: 4,
             spacing: 4,
         });
-        this._arrow = new Gtk.Arrow({
-            arrow_type: Gtk.ArrowType.RIGHT,
+        this._arrow = new Gtk.Image({
+            icon_name: 'pan-end-symbolic',
             no_show_all: true,
         });
         this._label = new Gtk.Label({
@@ -539,10 +539,10 @@ class UserListRow extends Gtk.ListBoxRow {
     _onExpandedChanged() {
         if (this._revealer.reveal_child) {
             this.get_style_context().add_class('expanded');
-            this._arrow.arrow_type = Gtk.ArrowType.DOWN;
+            this._arrow.icon_name = 'pan-down-symbolic';
         } else {
             this.get_style_context().remove_class('expanded');
-            this._arrow.arrow_type = Gtk.ArrowType.RIGHT;
+            this._arrow.icon_name = 'pan-end-symbolic';
             this._updateArrowVisibility();
         }
     }