Fix rust automatic-instrumentation.mdx (#8285)

* Update automatic-instrumentation.mdx

The tower rust docs state that the `Hub` layer should always come before the `Http` layer. 

https://docs.rs/sentry-tower/latest/sentry_tower/#usage-with-tower-http

The sentry docs should reflect this.

* Update src/platforms/rust/common/performance/instrumentation/automatic-instrumentation.mdx

Co-authored-by: Shana Matthews <shana.l.matthews@gmail.com>

---------

Co-authored-by: Shana Matthews <shana.l.matthews@gmail.com>

Author: danprueitt

src/platforms/rust/common/performance/instrumentation/automatic-instrumentation.mdx

@@ -50,13 +50,13 @@ fn main_span2() {
 
 The Sentry SDK offers an integration for the `tower` ecosystem which can automatically continue a trace from an incoming HTTP request.
 
+When combining both layers, order matters. For example, with tower::ServiceBuilder, you must define the Hub layer before the Http one, like so:
+
 ```rust
 use sentry_tower::{NewSentryLayer, SentryHttpLayer};
 use tower::ServiceBuilder;
 
 let layer = ServiceBuilder::new()
-    // continue trace from incoming request
-    .layer(SentryHttpLayer::with_transaction())
-    // bind a new hub for each request
-    .layer(NewSentryLayer::new_from_top());
+    .layer(NewSentryLayer::new_from_top())
+    .layer(SentryHttpLayer::with_transaction());
 ```