i18n: Fix several translation issues

References:
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http://i18n.osticket.com/translate/osticket-official/148/enus-de#4407
http://i18n.osticket.com/translate/osticket-official/148/enus-de#2379

include/class.email.php

@@ -253,7 +253,7 @@ class Email {
         if(!$vars['email'] || !Validator::is_email($vars['email'])) {
             $errors['email']=__('Valid email required');
         }elseif(($eid=Email::getIdByEmail($vars['email'])) && $eid!=$id) {
-            $errors['email']=__('Email already exits');
+            $errors['email']=__('Email already exists');
         }elseif($cfg && !strcasecmp($cfg->getAdminEmail(), $vars['email'])) {
             $errors['email']=__('Email already used as admin email!');
         }elseif(Staff::getIdByEmail($vars['email'])) { //make sure the email doesn't belong to any of the staff

scp/tickets.php

@@ -324,7 +324,7 @@ if($_POST && !$errors):
                         $msg=sprintf(__('Ticket flagged as unanswered by %s'),$thisstaff->getName());
                         $ticket->logActivity(__('Ticket Marked Unanswered'),$msg);
                     } else {
-                        $errors['err']=__('Problems marking the the ticket unanswered. Try again');
+                        $errors['err']=__('Problems marking the ticket unanswered. Try again');
                     }
                     break;
                 case 'banemail':