Fix heading order on subscribe-data page (#7739)

Author: hbuchel

src/pages/[platform]/build-a-backend/data/subscribe-data/index.mdx

@@ -340,9 +340,9 @@ func createSubscription() {
 
 </BlockSwitcher>
 
-### Unsubscribing from updates
+## Unsubscribing from updates
 
-#### Async/Await
+### Async/Await
 
 To unsubscribe from updates, you can call `cancel()` on the subscription.
 
@@ -353,7 +353,7 @@ func cancelSubscription() {
 }
 ```
 
-#### Combine
+### Combine
 
 Calling `cancel()` on the sequence will disconnect the subscription from the backend. Any downstream subscribers will also be cancelled.
 
@@ -537,7 +537,7 @@ Amplify.Hub.listen(
 );
 ```
 
-#### SubscriptionStatus
+### SubscriptionStatus
 
 - **`connected`** - Connected and working with no issues
 - **`connecting`** - Attempting to connect (both initial connection and reconnection)