Update modules/authentication/proc-enabling-authentication-with-github.adoc

Co-authored-by: Jessica He <[email protected]>

Author: themr0c

modules/authentication/proc-enabling-authentication-with-github.adoc

@@ -24,9 +24,6 @@ Enter your {product-short} authentication backend URL: `pass:c,a,q[{my-product-u
 
 Webhook URL:: Enter your {product-short} URL: `pass:c,a,q[{my-product-url}]`.
 
-Webhook secret::
-Not required.
-
 Repository permissions::
 Not required.