[Rules] Add header you can't modify or remove (#23073)

Author: pedrosousa

src/content/docs/rules/transform/request-header-modification/index.mdx

@@ -53,7 +53,7 @@ You can create a request header transform rule [in the dashboard](/rules/transfo
 
 - Due to protocol compliance reasons, modifying or removing request headers with [forbidden header names](https://developer.mozilla.org/en-US/docs/Glossary/Forbidden_header_name) (such as `Accept-Encoding`) is generally not allowed in Request Header Transform Rules.
 
-- You cannot modify the value of any header commonly used to identify the website visitor's IP address, such as `x-forwarded-for`, `true-client-ip`, or `x-real-ip`. Additionally, you cannot remove the `x-forwarded-for` header.
+- You cannot modify the value of any header commonly used to identify the website visitor's IP address or initial protocol, such as `x-forwarded-for`, `true-client-ip`, `x-real-ip`, or `x-forwarded-proto`. Additionally, you cannot remove the `x-forwarded-for` and `x-forwarded-proto` headers.
 
 - You cannot set or modify the value of `cookie` HTTP request headers, but you can remove these headers. Configuring a rule that removes the `cookie` HTTP request header will remove all `cookie` headers in matching requests.