erp5_corporate_identity_test: don't use index in select

bt5/erp5_corporate_identity_test/PathTemplateItem/portal_tests/template_test_zuite/testAndUpdateTestLetterEventTemplate.zpt

@@ -534,7 +534,7 @@ Note:
     <tr>
       <td>select</td>
       <td>name=field_your_portal_type
-      <td>index=5</td>
+      <td>Letter</td>
     </tr>
     <tr>
       <td>verifyTextPresent</td>