MDL-52843 users: Fix the PARAM type of the name fields in signup form

If editing the profile, the useredit_shared_definition() function set
the type of all name fields to PARAM_NOTAGS. This patch sets that type
consistently in the user signup form, too.

login/signup_form.php

@@ -63,7 +63,7 @@ function definition() {
         $namefields = useredit_get_required_name_fields();
         foreach ($namefields as $field) {
             $mform->addElement('text', $field, get_string($field), 'maxlength="100" size="30"');
-            $mform->setType($field, PARAM_TEXT);
+            $mform->setType($field, PARAM_NOTAGS);
             $stringid = 'missing' . $field;
             if (!get_string_manager()->string_exists($stringid, 'moodle')) {
                 $stringid = 'required';