add_filter( 'convert_content_for_amp', function( $the_content ) {
  
  // onmouseover属性を取り除く
  $the_content = preg_replace('/ +?onmouseover=["][^"]*?["]/i', '', $the_content);
  $the_content = preg_replace('/ +?onmouseover=[\'][^\']*?[\']/i', '', $the_content);
  
  // onmouseout 属性を取り除く
  $the_content = preg_replace('/ +?onmouseout=["][^"]*?["]/i', '', $the_content);
  $the_content = preg_replace('/ +?onmouseout=[\'][^\']*?[\']/i', '', $the_content);
  
  return $the_content;
});