Make <nav> tag in language switcher block accessible

Anysurfer reported that the NAV tag in language switcher block should be removed for accessibility purpose

<div id="<?php print $block_html_id; ?>" class="<?php print $classes; ?>"<?php print $attributes; ?>>
  <?php print render($title_prefix); ?>
  <?php if ($block->subject): ?>
    <h2<?php print $title_attributes; ?>><?php print $block->subject ?></h2>
  <?php endif; ?>
  <?php print render($title_suffix); ?>
  <nav<?php print $content_attributes; ?>>
  <?php print $content ?>
  </nav>
</div>