Invalid boolean values in recurring_events_create_form.js

Problem/Motivation

Commit 8fe75abb included several fixes for issues reported by phpcs, including changing true/false to TRUE/FALSE. Unfortunately, that change was also applied to recurring_events_create_form.js, causing an error because TRUE and FALSE are not recognized keywords in JavaScript

Steps to reproduce

1. Open your browser's JS console.
2. Go to the event creation form (/events/add/default).
3. Select "Weekly" recurrence.
4. Set the start date.

Result: Console reports Uncaught ReferenceError: FALSE is not defined

Proposed resolution

Revert FALSE to false and TRUE to true in js/recurring_events_create_form.js.