help: Add '...' to indicate there will be another dialog

Change-Id: Ic884acf20f1d1a48f5306b380338fd0a99d63fa8
Reviewed-by: hjk <qthjk@ovi.com>

src/plugins/help/docsettingspage.ui

@@ -44,7 +44,7 @@
         <item>
          <widget class="QPushButton" name="addButton">
           <property name="text">
-           <string>Add</string>
+           <string>Add...</string>
           </property>
          </widget>
         </item>