Removing to_json() function from docs builds until it's added to the system catalog (#3303)

gpdb-doc/dita/admin_guide/query/topics/json-data.xml

@@ -235,6 +235,7 @@ SELECT '{"foo": [true, "bar"], "tags": {"a": 1, "b": null}}'::json;</pre>
               </row>
             </thead>
             <tbody>
+<!--
               <row>
                 <entry><codeph>to_json(anyelement)</codeph></entry>
                 <entry>Returns the value as a valid JSON object. Arrays and composites are processed
@@ -251,6 +252,7 @@ SELECT '{"foo": [true, "bar"], "tags": {"a": 1, "b": null}}'::json;</pre>
                   <codeph>"Fred said \"Hi.\""</codeph>
                 </entry>
               </row>
+-->
               <row>
                 <entry><codeph>array_to_json(anyarray [, pretty_bool])</codeph></entry>
                 <entry>Returns the array as a JSON array. A Greenplum Database multidimensional
@@ -277,10 +279,12 @@ SELECT '{"foo": [true, "bar"], "tags": {"a": 1, "b": null}}'::json;</pre>
             </tbody>
           </tgroup>
         </table>
+<!--
         <note><codeph>array_to_json</codeph> and <codeph>row_to_json</codeph> have the same behavior
           as <codeph>to_json</codeph> except for offering a pretty-printing option. The behavior
           described for <codeph>to_json</codeph> also applies to individual values converted by the
           other JSON creation functions.</note>
+-->
       </body>
     </topic>
     <topic id="topic_z5d_snw_2z">

gpdb-doc/dita/ref_guide/function-summary.xml

@@ -604,6 +604,7 @@ SELECT foo();
               </row>
             </thead>
             <tbody>
+<!--
               <row>
                 <entry><codeph>to_json(anyelement)</codeph></entry>
                 <entry>Returns the value as a valid JSON object. Arrays and composites are processed
@@ -620,6 +621,7 @@ SELECT foo();
                   <codeph>"Fred said \"Hi.\""</codeph>
                 </entry>
               </row>
+ -->
               <row>
                 <entry><codeph>array_to_json(anyarray [, pretty_bool])</codeph></entry>
                 <entry>Returns the array as a JSON array. A Greenplum Database multidimensional
@@ -646,10 +648,12 @@ SELECT foo();
             </tbody>
           </tgroup>
         </table>
+<!--
         <note><codeph>array_to_json</codeph> and <codeph>row_to_json</codeph> have the same behavior
           as <codeph>to_json</codeph> except for offering a pretty-printing option. The behavior
           described for <codeph>to_json</codeph> also applies to individual values converted by the
           other JSON creation functions.</note>
+-->
       </body>
     </topic>
     <topic id="topic_z5d_snw_2z">