ntp: fix a typo spotted by pavelb

(cherry picked from commit 6b39cd2e)

src/www/services_ntpd_gps.php

@@ -331,7 +331,7 @@ SureGPS =    #Sure Electronics SKG16B
                           <?=gettext("This option allows you to select a predefined configuration.");?>
                           <br />
                           <strong><?=gettext("Note: ");?></strong><?=gettext("Select Generic if your GPS is not listed."); ?><br />
-                          <strong><?=gettext("Note: ");?></strong><?=gettext("The perdefined configurations assume your GPS has already been set to NMEA mode."); ?>
+                          <strong><?=gettext("Note: ");?></strong><?=gettext("The predefined configurations assume your GPS has already been set to NMEA mode."); ?>
                         </div>
                       </td>
                     </tr>