erp5_core: fix field's title to respect naming conventions

product/ERP5/bootstrap/erp5_core/SkinTemplateItem/portal_skins/erp5_core/Preference_viewHtmlStyle/my_preferred_whitespace_number_for_child_item_indentation.xml

@@ -85,7 +85,7 @@
                 </item>
                 <item>
                     <key> <string>title</string> </key>
-                    <value> <string>Preferred Whitespace Number For Indentation</string> </value>
+                    <value> <string>Preferred Whitespace Number for Indentation</string> </value>
                 </item>
               </dictionary>
             </value>