Fix wrong xml:id on the fieldsynopsis element of Exception::$code

Author: kocsismate

language/predefined/exception.xml

@@ -43,7 +43,7 @@
      <varname linkend="exception.props.string">string</varname>
      <initializer>""</initializer>
     </fieldsynopsis>
-    <fieldsynopsis xml:id="class.exception..code">
+    <fieldsynopsis>
      <modifier>protected</modifier>
      <type>int</type>
      <varname linkend="exception.props.code">code</varname>