MDL-81522 phpunit: Add missing void return type to all tests

While this change is not 100% required now, it's good habit
and we are checking for it since Moodle 4.4.

All the changes in this commit have been applied automatically
using the moodle.PHPUnit.TestReturnType sniff and are, exclusively
adding the ": void" return types when missing.

user/tests/editlib_test.php

@@ -34,7 +34,7 @@ class editlib_test extends \advanced_testcase {
     /**
      * Test that the required fields are returned in the correct order.
      */
-    function test_useredit_get_required_name_fields() {
+    function test_useredit_get_required_name_fields(): void {
         global $CFG;
         // Back up config settings for restore later.
         $originalcfg = new \stdClass();
@@ -60,7 +60,7 @@ class editlib_test extends \advanced_testcase {
     /**
      * Test that the enabled fields are returned in the correct order.
      */
-    function test_useredit_get_enabled_name_fields() {
+    function test_useredit_get_enabled_name_fields(): void {
         global $CFG;
         // Back up config settings for restore later.
         $originalcfg = new \stdClass();
@@ -86,7 +86,7 @@ class editlib_test extends \advanced_testcase {
     /**
      * Test that the disabled fields are returned.
      */
-    function test_useredit_get_disabled_name_fields() {
+    function test_useredit_get_disabled_name_fields(): void {
         global $CFG;
         // Back up config settings for restore later.
         $originalcfg = new \stdClass();