doc: Improve wording and fix whitespace

Author: petere

doc/src/sgml/logical-replication.sgml

@@ -66,11 +66,11 @@
 
    <listitem>
     <para>
-     Replicating between cross platform PostgreSQL instances (for example
-     Linux to Windows)
+     Replicating between PostgreSQL instances on different platforms (for
+     example Linux to Windows)
     </para>
    </listitem>
-   
+
    <listitem>
     <para>
      Giving access to replicated data to different groups of users.