Thats WordPress default usage.. Just remove the content within the brackets:
<nav id="nav-single">
<h3 class="assistive-text"><?php _e( 'Post navigation', 'admired' ); ?></h3>
<span class="nav-previous"><?php previous_post_link(); ?></span>
<span class="nav-next"><?php next_post_link(); ?></span>
</nav><!-- #nav-single -->