[Fixes #GeoNode#6772] Remove Open Data Link (GeoNode#6787)

Remove the link as the Open Data endpoint does not exist anymore

Author: t-book

geonode/templates/developer.html

@@ -88,10 +88,6 @@ <h3>{% trans "GeoNode's Web Services" %}</h3>
         <td><strong>{% trans "Metadata search via OAI-PMH:" %}</strong></td>
         <td><a href="{{CATALOGUE_BASE_URL}}?mode=oaipmh&verb=Identify">OAI-PMH 2.0</a></td>
       </tr>
-      <tr>
-        <td><strong>{% trans "Open Data:" %}</strong></td>
-        <td><a href="{{SITEURL}}/data.json">data.json</a></td>
-      </tr>
       <tr>
         <td><strong>{% trans "Cached tiles via WMTS:" %}</strong></td>
         <td><a href="{{GEOSERVER_BASE_URL}}gwc/service/wmts?service=WMTS&version=1.0.0&request=GetCapabilities">WMTS 1.0.0</a></td>