[class-properties] Remove unnecessary return and temp variable (#8123)

* Remove unnecessary temp variable

* Update tests

packages/babel-plugin-transform-classes/test/fixtures/spec/super-call-only-allowed-in-derived-constructor/output.js

@@ -0,0 +1,9 @@
+function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }
+
+let Foo = function Foo() {
+  "use strict";
+
+  _classCallCheck(this, Foo);
+
+  super();
+};