data/ui: Reword "revert" to "discard" in confirmation dialog

This is partially because we're reusing this now for confirmation on
encoding change, but also because it's actually a better description of
what we want to confirm. We don't want to confirm whether the user wants
to revert... we want to confirm whether they want to discard their
current changes. That's the destructive part of the operation.

Author: kaiw

data/ui/filediff.ui

@@ -833,7 +833,7 @@
     <property name="type_hint">dialog</property>
     <property name="skip_taskbar_hint">True</property>
     <property name="message_type">question</property>
-    <property name="text" translatable="yes">Revert unsaved changes to documents?</property>
+    <property name="text" translatable="yes">Discard unsaved changes to documents?</property>
     <property name="secondary_text" translatable="yes">Changes made to the following documents will be permanently lost:</property>
     <child internal-child="vbox">
       <object class="GtkBox" id="dialog-vbox2">
@@ -863,12 +863,11 @@
             </child>
             <child>
               <object class="GtkButton" id="revert_button">
-                <property name="label">gtk-revert-to-saved</property>
+                <property name="label" translatable="yes">_Discard</property>
                 <property name="visible">True</property>
                 <property name="can_focus">True</property>
                 <property name="receives_default">True</property>
                 <property name="use_underline">True</property>
-                <property name="use_stock">True</property>
               </object>
               <packing>
                 <property name="expand">False</property>