setting-dialog: fix typo

Change-Id: Idf1b56418af4e8f58986b354183f65fbcea2ae03
Refs: #2482
diff --git a/src/setting-dialog.ui b/src/setting-dialog.ui
index dc5301b..da8ca94 100644
--- a/src/setting-dialog.ui
+++ b/src/setting-dialog.ui
@@ -74,7 +74,7 @@
          </font>
         </property>
         <property name="text">
-         <string>routbale prefix:</string>
+         <string>routable prefix:</string>
         </property>
        </widget>
       </item>