Bug 1698668 - Replace tabs with spaces in this test. r=harry

Depends on D108547

Differential Revision: https://phabricator.services.mozilla.com/D108548

widget/tests/standalone_native_menu_window.xhtml

@@ -27,17 +27,17 @@
   <popupset>
     <menupopup id="standalonenativemenu">
       <menu id="foo" label="Foo">
-	<menupopup>
-	  <menuitem label="FooItem0" command="cmd_FooItem0"/>
-	  <menuitem label="FooItem1" command="cmd_FooItem1"/>
-	  <menuseparator/>
-	  <menu label="Bar">
+        <menupopup>
+          <menuitem label="FooItem0" command="cmd_FooItem0"/>
+          <menuitem label="FooItem1" command="cmd_FooItem1"/>
+          <menuseparator/>
+          <menu label="Bar">
             <menupopup>
               <menuitem label="BarItem0" command="cmd_BarItem0"/>
               <menuitem label="BarItem1" command="cmd_BarItem1"/>
             </menupopup>
-	  </menu>
-	</menupopup>
+          </menu>
+        </menupopup>
       </menu>
     </menupopup>
   </popupset>