Doc: fix oversights in "Client/Server Character Set Conversions" table.

This table claimed that JOHAB could be used as a server encoding, which
was true originally but hasn't been true since 8.3.  It also lacked
entries for EUC_JIS_2004 and SHIFT_JIS_2004.

JOHAB problem noted by Lars Kanis, the others by me.

Discussion: https://postgr.es/m/c0f514a1-b7a9-b9ea-1c02-c34aead56c06@greiz-reinsdorf.de

doc/src/sgml/charset.sgml

@@ -1483,6 +1483,13 @@ $ <userinput>psql -l</userinput>
          <literal>UTF8</literal>
          </entry>
         </row>
+        <row>
+         <entry><literal>EUC_JIS_2004</literal></entry>
+         <entry><emphasis>EUC_JIS_2004</emphasis>,
+         <literal>SHIFT_JIS_2004</literal>,
+         <literal>UTF8</literal>
+         </entry>
+        </row>
         <row>
          <entry><literal>EUC_KR</literal></entry>
          <entry><emphasis>EUC_KR</emphasis>,
@@ -1538,8 +1545,7 @@ $ <userinput>psql -l</userinput>
         </row>
         <row>
          <entry><literal>JOHAB</literal></entry>
-         <entry><emphasis>JOHAB</emphasis>,
-         <literal>UTF8</literal>
+         <entry><emphasis>not supported as a server encoding</emphasis>
          </entry>
         </row>
         <row>
@@ -1645,6 +1651,11 @@ $ <userinput>psql -l</userinput>
          <entry><emphasis>not supported as a server encoding</emphasis>
          </entry>
         </row>
+        <row>
+         <entry><literal>SHIFT_JIS_2004</literal></entry>
+         <entry><emphasis>not supported as a server encoding</emphasis>
+         </entry>
+        </row>
         <row>
          <entry><literal>SQL_ASCII</literal></entry>
          <entry><emphasis>any (no conversion will be performed)</emphasis>