[seahorse] PGP: use proper icon name for "Expire" button.

[Niels De Graef <nielsdg src gnome org>]

commit e620e7ed9ffdb6dde199701bc5a62706cdd0d32b
Author: Niels De Graef <nielsdegraef gmail com>
Date:   Fri Aug 3 02:58:11 2018 +0200

    PGP: use proper icon name for "Expire" button.
    
    The freedeskop specifies "x-office-calendar" as officially supported.
    
    Fixes [bug 757237](https://bugzilla.gnome.org/show_bug.cgi?id=757237)

 pgp/seahorse-pgp-private-key-properties.ui | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/pgp/seahorse-pgp-private-key-properties.ui b/pgp/seahorse-pgp-private-key-properties.ui
index c1805d32..18eaf517 100644
--- a/pgp/seahorse-pgp-private-key-properties.ui
+++ b/pgp/seahorse-pgp-private-key-properties.ui
@@ -1277,7 +1277,7 @@
                                             <child>
                                               <object class="GtkImage" id="image49">
                                                 <property name="visible">True</property>
-                                                <property name="icon_name">stock_calendar</property>
+                                                <property name="icon_name">x-office-calendar</property>
                                               </object>
                                             </child>
                                           </object>
@@ -1567,7 +1567,7 @@
                                         <child>
                                           <object class="GtkImage" id="image30">
                                             <property name="visible">True</property>
-                                            <property name="icon_name">stock_calendar</property>
+                                            <property name="icon_name">x-office-calendar</property>
                                           </object>
                                           <packing>
                                             <property name="expand">False</property>