Fix method name typo in EventHandlers.java

**PR Breakdown:**
This PR fixes a typo in the name of an event handler. Its current name is `onDisalow` while it should actually be `onDisallow`. This PR addresses this severe flaw in the plugin.

**Justification:**
Typos look unprofessional and must be defeated. Also, with this project being open-source, it could lead to beginners learning wrong ways of spelling 'disallow'.

Thank you!