Remove outdated http.request.header.host guidance (#479)

Co-authored-by: Alexander Wert <AlexanderWert@users.noreply.github.com>

CHANGELOG.md

@@ -50,6 +50,8 @@ release.
   ([#469](https://github.com/open-telemetry/semantic-conventions/pull/469))
 - Change `network.protocol.name` from opt-in to conditionally required.
   ([#478](https://github.com/open-telemetry/semantic-conventions/pull/478))
+- Remove outdated `http.request.header.host` guidance
+  ([#479](https://github.com/open-telemetry/semantic-conventions/pull/479))
 
 ### Features
 

docs/http/http-spans.md

@@ -256,8 +256,6 @@ Following attributes MUST be provided **at span creation time** (when provided a
 * [`url.full`](../attributes-registry/url.md)
 <!-- endsemconv -->
 
-Note that in some cases host and port identifiers in the `Host` header might be different from the `server.address` and `server.port`, in this case instrumentation MAY populate `Host` header on `http.request.header.host` attribute even if it's not enabled by user.
-
 ### HTTP client span duration
 
 There are some minimal constraints that SHOULD be honored:
@@ -380,8 +378,6 @@ Following attributes MUST be provided **at span creation time** (when provided a
 
 `http.route` MUST be provided at span creation time if and only if it's already available. If it becomes available after span starts, instrumentation MUST populate it anytime before span ends.
 
-Note that in some cases host and port identifiers in the `Host` header might be different from the `server.address` and `server.port`, in this case instrumentation MAY populate `Host` header on `http.request.header.host` attribute even if it's not enabled by user.
-
 ## Examples
 
 ### HTTP client-server example