Clarifies usage of trusted_proxies (#18447)

* Clarifies usage of trusted_proxies

As discussed in home-assistant/core#52736

* Tweak

Co-authored-by: Franck Nijhof <frenck@frenck.nl>

source/_integrations/http.markdown

@@ -64,7 +64,7 @@ use_x_forwarded_for:
   type: boolean
   default: false
 trusted_proxies:
-  description: "List of trusted proxies, consisting of IP addresses or networks, that are allowed to set the `X-Forwarded-For` header.  This is required when using `use_x_forwarded_for` because all requests to Home Assistant, regardless of source, will arrive from the reverse proxy IP address. Therefore in a reverse proxy scenario, this option should be set with extreme care."
+  description: "List of trusted proxies, consisting of IP addresses or networks, that are allowed to set the `X-Forwarded-For` header.  This is required when using `use_x_forwarded_for` because all requests to Home Assistant, regardless of source, will arrive from the reverse proxy IP address. Therefore in a reverse proxy scenario, this option should be set with extreme care. If the immediate upstream proxy is not in the list, the request will be rejected. If any other intermediate proxy is not in the list, the first untrusted proxy will be considered the client."
   required: false
   type: [string, list]
 ip_ban_enabled: