I commented it out using the website editor.

Customize -> HTML Editor -> - Layout (In the dropdown menu)

Comment the following lines adding <!--  --> 

 <!--<li groups="base.group_website_publisher">
                <t t-set="url_return" t-value="url_for('', '[lang]') + '?' + keep_query()"/>
                <a t-attf-href="/web#action=base.action_view_base_language_install&amp;website_id=#{website.id if website else ''}&amp;url_return=#{url_return}">
                    <i class="fa fa-plus-circle"/>
                    Add a language...
                </a>
            </li>-->