migration84: Add missing space

Author: TimWolla

appendices/migration84/incompatible.xml

@@ -235,7 +235,7 @@
      <member><function>d<replaceable>*</replaceable>gettext</function></member>
     </simplelist>
     now throw a <exceptionname>ValueError</exceptionname> if
-    <parameter>domain</parameter>is the empty string.
+    <parameter>domain</parameter> is the empty string.
    </para>
   </sect3>