Make translatable the auth-username-label in lock-dialog-default.ui

Author: rbuj

data/lock-dialog-default.ui

@@ -97,7 +97,7 @@
                       <object class="GtkLabel" id="auth-username-label">
                         <property name="visible">True</property>
                         <property name="can_focus">False</property>
-                        <property name="label">&lt;span size="small"&gt;%U on %h&lt;/span&gt;</property>
+                        <property name="label" translatable="yes">&lt;span size="small"&gt;%U on %h&lt;/span&gt;</property>
                         <property name="use_markup">True</property>
                       </object>
                       <packing>