Minor fix on doc theme version 1.3.7.7

Hi.

At doc theme, file 404.php is a typo on line 13

<p><?php _e('If you're lazy, or don't feel social, you could', 'doc'); ?>:</p>

single quotes into _e(‘.

Replaced the line with

<p><?php _e("If you're lazy, or don't feel social, you could", "doc"); ?>:</p>

Cheers Lena