Remove redundant monitor-address key (it's in the <zeo> section).

src/ZEO/schema.xml

@@ -16,14 +16,6 @@
 
   <section type="zeo" name="*" required="yes" attribute="zeo" />
 
-  <key name="monitor-address" datatype="socket-address" required="no">
-    <description>
-      The address at which the monitor server should listen.  If
-      specified, a monitor server is started.  The monitor server
-      provides server statistics in a simple text format.
-    </description>
-  </key>
-
   <multisection name="+" type="storage"
                 attribute="storages"
                 required="yes">