chore: remove duplicate h1

The `title` is already being added to the page as an `<h1>`. This is
showing as a duplicate

Author: C-Mejlak

certificate-manager/webhook-events.mdx

@@ -5,7 +5,6 @@ description: Smallstep Platform Webhook Events provide observability around cert
 ---
 
 
-# Webhook Events
 Webhook Events allow for real-time logging of SSH sessions, 
 
 certificate creation, and certificate expirations events.