doc: Fix man page whitespace issues

Whitespace between tags is significant, and in some cases it creates
extra vertical space in man pages.  The fix is to remove some newlines
in the markup.

doc/src/sgml/ref/cluster.sgml

@@ -28,7 +28,6 @@ CLUSTER [VERBOSE]
 <phrase>where <replaceable class="parameter">option</replaceable> can be one of:</phrase>
 
     VERBOSE [ <replaceable class="parameter">boolean</replaceable> ]
-
 </synopsis>
  </refsynopsisdiv>
 

doc/src/sgml/ref/create_extension.sgml

@@ -223,8 +223,7 @@ CREATE EXTENSION hstore SCHEMA addons;
 <programlisting>
 SET search_path = addons;
 CREATE EXTENSION hstore;
-</programlisting>
-  </para>
+</programlisting></para>
  </refsect1>
 
  <refsect1>

doc/src/sgml/ref/create_procedure.sgml

@@ -382,8 +382,7 @@ END;
    and call like this:
 <programlisting>
 CALL insert_data(1, 2);
-</programlisting>
-  </para>
+</programlisting></para>
  </refsect1>
 
  <refsect1 id="sql-createprocedure-compat">