MDL-51371 course: fix core_course_get_course_module assertion

A recent bugfix before integration left this failing. They are 22.

course/tests/externallib_test.php

@@ -1550,7 +1550,7 @@ class core_course_externallib_testcase extends externallib_advanced_testcase {
 
         $this->assertCount(0, $result['warnings']);
         // Test we retrieve all the fields.
-        $this->assertCount(21, $result['cm']);
+        $this->assertCount(22, $result['cm']);
         $this->assertEquals($record['name'], $result['cm']['name']);
         $this->assertEquals($options['idnumber'], $result['cm']['idnumber']);