[WAF]Update firewall-rules-to-custom-rules.mdx

Its a zone level feature.

Author: nenizera

src/content/docs/waf/reference/migration-guides/firewall-rules-to-custom-rules.mdx

@@ -43,7 +43,7 @@ Custom block response configurations will not be returned by the Firewall Rules
 
 ### Different error page for blocked requests
 
-Requests blocked by a firewall rule with a _Block_ action would get a Cloudflare [1020 error code](/support/troubleshooting/cloudflare-errors/troubleshooting-cloudflare-1xxx-errors/#error-1020-access-denied) response. Cloudflare users could customize this error page in **Custom Pages** > **1000 Class Errors**.
+Requests blocked by a firewall rule with a _Block_ action would get a Cloudflare [1020 error code](/support/troubleshooting/cloudflare-errors/troubleshooting-cloudflare-1xxx-errors/#error-1020-access-denied) response. Cloudflare users could customize this error page in **Zone** > **Custom Pages** > **1000 Class errors**.
 
 Requests blocked by a WAF custom rule will get a different response: the WAF block response. To customize the default block response, you can either: