MDL-68388 grade: Tidy comments and whitespace

grade/edit/letter/index.php

@@ -229,10 +229,8 @@ if (!$edit) {
             }
         }
 
-        // Cache the changed letters.
         if (!empty($letters)) {
-            // For some reason, the cache saves it in the order in which they were entered
-            // but we really want to order them in descending order so we sort it here.
+            // Ensure that the letters are correctly sorted.
             krsort($letters);
             $cache->set($context->id, $letters);
         }

lib/tests/gradelib_test.php

@@ -249,8 +249,7 @@ class core_gradelib_testcase extends advanced_testcase {
     /**
      * Test the caching of grade letters.
      */
-    public function test_get_grade_letters() {
-
+    public function test_get_grade_letters(): void {
         $this->resetAfterTest();
 
         $course = $this->getDataGenerator()->create_course();
@@ -273,7 +272,7 @@ class core_gradelib_testcase extends advanced_testcase {
     /**
      * Test custom letters.
      */
-    public function test_get_grade_letters_custom() {
+    public function test_get_grade_letters_custom(): void {
         global $DB;
 
         $this->resetAfterTest();