Image fields do not have 'rel' property removed

<div class="field-item even" rel="og:image rdfs:seeAlso"> on line 11
- The attribute 'rel' may not appear in tag 'div'.
   [code: DISALLOWED_ATTR  category: DISALLOWED_HTML]
   ACTION TAKEN: div.rel attribute was removed due to validation issues.

I could not remove this property using amptheme_preprocess_field().

This rdf attribute is set when you install using the standard install profile: https://api.drupal.org/api/drupal/profiles%21standard%21standard.install...

  // Insert default pre-defined RDF mapping into the database.
  $rdf_mappings = array(
    array(
      'type' => 'node',
      'bundle' => 'page',
      'mapping' => array(
        'rdftype' => array('foaf:Document'),
      ),
    ),
    array(
      'type' => 'node',
      'bundle' => 'article',
      'mapping' => array(
        'field_image' => array(
          'predicates' => array('og:image', 'rdfs:seeAlso'),
          'type' => 'rel',
        ),
        'field_tags' => array(
          'predicates' => array('dc:subject'),
          'type' => 'rel',
        ),
      ),
    ),
  );
  foreach ($rdf_mappings as $rdf_mapping) {
    rdf_mapping_save($rdf_mapping);
  }