Properly capitalize the TimeZone parameter

For better or worse, it is implemented in mixed case, so document it
as such, at least in the main listing, like DateStyle.

Josh Kupershmidt

doc/src/sgml/config.sgml

@@ -5151,10 +5151,10 @@ SET XML OPTION { DOCUMENT | CONTENT };
       </listitem>
      </varlistentry>
 
-     <varlistentry id="guc-timezone" xreflabel="timezone">
-      <term><varname>timezone</varname> (<type>string</type>)</term>
+     <varlistentry id="guc-timezone" xreflabel="TimeZone">
+      <term><varname>TimeZone</varname> (<type>string</type>)</term>
       <indexterm>
-       <primary><varname>timezone</> configuration parameter</primary>
+       <primary><varname>TimeZone</> configuration parameter</primary>
       </indexterm>
       <indexterm><primary>time zone</></>
       <listitem>