Fix typo

Author: thom

interface/web/admin/lib/lang/en_system_config.lng

@@ -73,7 +73,7 @@ $wb['customer_no_template_error_regex_txt'] = 'The customer No. template contain
 $wb['customer_no_start_txt'] = 'Customer No. start value';
 $wb['customer_no_counter_txt'] = 'Customer No. counter';
 $wb['session_timeout_txt'] = 'Session timeout (minutes)';
-$wb['session_allow_endless_txt'] = 'Enable 'stay logged in'';
+$wb['session_allow_endless_txt'] = 'Enable "stay logged in"';
 $wb['No'] = 'No';
 $wb['min_password_length_txt'] = 'Minimum password length';
 $wb['min_password_strength_txt'] = 'Minimum password strength';