minor: fix typo in comment

Author: romani

src/xdocs/config_reporting.xml

@@ -73,7 +73,7 @@
     <section name="Enable External DTD load">
       <p>
         The property <code>checkstyle.enableExternalDtdLoad</code>
-        defines ability use custom DTD files inconfig and load them from some location.
+        defines ability use custom DTD files in config and load them from some location.
         The property type
         is <a href="property_types.html#boolean">boolean</a> and defaults
         to <code>false</code>.